chore!: depositAmount and minimumStake naming (#16148)

Addressing feedback from @benesjan. Also using his prompt idea to see
how well it works.

--- 
## Summary

This PR refactors validator staking terminology throughout the Aztec
codebase to improve clarity and better reflect the purpose of key
staking parameters. The main changes involve renaming `depositAmount` to
`activationThreshold` and `minimumStake` to `ejectionThreshold`, along
with related library and method renames.

## Key Changes

### Parameter Renames
- **`depositAmount` → `activationThreshold`**: The amount of tokens
required to activate a validator and join the validator set
- **`minimumStake` → `ejectionThreshold`**: The minimum token balance
below which a validator is ejected from the active set

### Contract & Library Updates
- **Solidity Contracts**: Updated all references in `Rollup.sol`,
`IStaking.sol`, `GSE.sol`, and related contracts
- **Libraries**: 
- `UserLib` → `CheckpointedUintLib` (more descriptive name for
checkpoint management)
  - `DelegationLib` → `StakeDelegationLib` (clearer purpose indication)
- **Methods**: `finaliseHelper()` → `finaliseWithdraw()` in GSE contract
for better clarity

### Configuration & Environment Variables
- Updated environment variables:
  - `AZTEC_DEPOSIT_AMOUNT` → `AZTEC_ACTIVATION_THRESHOLD`
  - `AZTEC_MINIMUM_STAKE` → `AZTEC_EJECTION_THRESHOLD`
- Updated all configuration files, test constants, and deployment
scripts

### Documentation
- Updated CLI reference documentation to reflect new parameter names
- Updated all code comments to use the new terminology

## Benefits

1. **Improved Clarity**: The new names clearly indicate the purpose of
each parameter - one for entering the validator set, one for being
removed from it
2. **Better Developer Experience**: Developers can immediately
understand what these thresholds represent without needing additional
context
3. **Consistency**: Uniform terminology across the entire codebase
reduces confusion
4. **Future-Proof**: The new names are more generic and adaptable to
potential future staking mechanism changes

## Breaking Changes

⚠️ **This is a breaking change** that affects:

1. **Environment Variables**: Any deployment or configuration using the
old environment variable names (`AZTEC_DEPOSIT_AMOUNT`,
`AZTEC_MINIMUM_STAKE`) must be updated
2. **Contract Interfaces**: External systems calling
`getDepositAmount()`, `getMinimumStake()`, or `finaliseHelper()` must
update to use the new method names
3. **Configuration Files**: Any JSON/YAML configuration files using the
old parameter names need updates
4. **Deployment Scripts**: Custom deployment scripts referencing the old
names will need modification

### Migration Guide
- Replace `depositAmount` with `activationThreshold` in all
configurations
- Replace `minimumStake` with `ejectionThreshold` in all configurations
- Update contract calls:
  - `getDepositAmount()` → `getActivationThreshold()`
  - `getMinimumStake()` → `getEjectionThreshold()`
  - `finaliseHelper()` → `finaliseWithdraw()`

Author: LHerskind

docs/docs/the_aztec_network/guides/run_nodes/cli_reference.md

@@ -381,10 +381,10 @@ If two subsystems can contain the same configuration option, only one needs to b
     --archiver.aztecProofSubmissionEpochs <value>                  (default: 1)                                                  ($AZTEC_PROOF_SUBMISSION_EPOCHS)
           The number of epochs after an epoch ends that proofs are still accepted.
 
-    --archiver.depositAmount <value>                               (default: 100000000000000000000)                              ($AZTEC_DEPOSIT_AMOUNT)
+    --archiver.activationThreshold <value>                               (default: 100000000000000000000)                              ($AZTEC_ACTIVATION_THRESHOLD)
           The deposit amount for a validator
 
-    --archiver.minimumStake <value>                                (default: 50000000000000000000)                               ($AZTEC_MINIMUM_STAKE)
+    --archiver.ejectionThreshold <value>                                (default: 50000000000000000000)                               ($AZTEC_EJECTION_THRESHOLD)
           The minimum stake for a validator.
 
     --archiver.slashingQuorum <value>                              (default: 101)                                                ($AZTEC_SLASHING_QUORUM)

l1-contracts/script/InternalGov.s.sol

@@ -84,7 +84,9 @@ contract GovScript is Test {
     emit log_named_uint(
       "\tNumber of attestors ", IStaking(address(rollup)).getActiveAttesterCount()
     );
-    emit log_named_decimal_uint("\tMinimum stake", IStaking(address(rollup)).getDepositAmount(), 18);
+    emit log_named_decimal_uint(
+      "\tMinimum stake", IStaking(address(rollup)).getActivationThreshold(), 18
+    );
 
     emit log_named_address("# Governance", address(governance));
     Configuration memory config = governance.getConfiguration();

l1-contracts/src/core/Rollup.sol

@@ -224,12 +224,12 @@ contract Rollup is IStaking, IValidatorSelection, IRollup, RollupCore {
     return StakingLib.getStorage().stakingAsset;
   }
 
-  function getMinimumStake() external view override(IStaking) returns (uint256) {
-    return StakingLib.getStorage().gse.MINIMUM_STAKE();
+  function getEjectionThreshold() external view override(IStaking) returns (uint256) {
+    return StakingLib.getStorage().gse.EJECTION_THRESHOLD();
   }
 
-  function getDepositAmount() external view override(IStaking) returns (uint256) {
-    return StakingLib.getStorage().gse.DEPOSIT_AMOUNT();
+  function getActivationThreshold() external view override(IStaking) returns (uint256) {
+    return StakingLib.getStorage().gse.ACTIVATION_THRESHOLD();
   }
 
   function getExitDelay() external view override(IStaking) returns (Timestamp) {

l1-contracts/src/core/interfaces/IStaking.sol

@@ -37,8 +37,8 @@ interface IStaking is IStakingCore {
   function getAttesterAtIndex(uint256 _index) external view returns (address);
   function getSlasher() external view returns (address);
   function getStakingAsset() external view returns (IERC20);
-  function getDepositAmount() external view returns (uint256);
-  function getMinimumStake() external view returns (uint256);
+  function getActivationThreshold() external view returns (uint256);
+  function getEjectionThreshold() external view returns (uint256);
   function getExitDelay() external view returns (Timestamp);
   function getGSE() external view returns (GSE);
   function getAttesterView(address _attester) external view returns (AttesterView memory);

l1-contracts/src/core/libraries/rollup/StakingLib.sol

@@ -150,7 +150,7 @@ library StakingLib {
 
     delete store.exits[_attester];
 
-    store.gse.finaliseHelper(exit.withdrawalId);
+    store.gse.finaliseWithdraw(exit.withdrawalId);
     store.stakingAsset.transfer(exit.recipientOrWithdrawer, exit.amount);
 
     emit IStakingCore.WithdrawFinalised(_attester, exit.recipientOrWithdrawer, exit.amount);
@@ -225,7 +225,7 @@ library StakingLib {
     StakingStorage storage store = getStorage();
     // We don't allow deposits, if we are currently exiting.
     require(!store.exits[_attester].exists, Errors.Staking__AlreadyExiting(_attester));
-    uint256 amount = store.gse.DEPOSIT_AMOUNT();
+    uint256 amount = store.gse.ACTIVATION_THRESHOLD();
 
     store.stakingAsset.transferFrom(msg.sender, address(this), amount);
     store.entryQueue.enqueue(_attester, _withdrawer, _moveWithLatestRollup);
@@ -243,7 +243,7 @@ library StakingLib {
       store.nextFlushableEpoch <= currentEpoch, Errors.Staking__QueueAlreadyFlushed(currentEpoch)
     );
     store.nextFlushableEpoch = currentEpoch + Epoch.wrap(1);
-    uint256 amount = store.gse.DEPOSIT_AMOUNT();
+    uint256 amount = store.gse.ACTIVATION_THRESHOLD();
 
     uint256 queueLength = store.entryQueue.length();
     uint256 numToDequeue = Math.min(_maxAddableValidators, queueLength);