feat: public data tree overrides for simulation

[dbanks12]

Extends SimulationOverrides with a publicStorage field, plumbed through .simulate({ overrides }) on aztec.js → wallet → PXE → AztecNode.simulatePublicCalls. Each entry writes a (contract, slot, value) into the public-data tree of the ephemeral world-state fork before the tx runs; real chain state is untouched.

const result = await contract.methods.read_balance(account).simulate({
  overrides: {
    publicStorage: [{ contract: contract.address, slot: BALANCE_SLOT, value: new Fr(1_000_000n) }],
  },
});

Test plan

• Unit tests in aztec-node/src/aztec-node/public_data_overrides.test.ts.
• E2E e2e_avm_simulator publicDataOverrides describe block.
• migration_notes.md and how_to_test.md updated.

[dbanks12]

• feat: expose wallet.registerContractClass (prep for simulating contract upgrades) #22932 : 4 dependent PRs (#22833 , #23016 , #23045 and 1 other)
• feat: public data tree overrides for simulation #22830 👈 (View in Graphite)
• refactor: drop artifact field from SimulationOverrides #22957
• merge-train/fairies

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[dbanks12]

if we know for certain that we'll never want to override state from other trees, we could flatten this and just have "public storage overrides" instead of generic "state overrides"

[Thunkar]

Won't block, but as discussed I'd try to lean more into a consolidated overrides object, since very soon we'll be able to do contracts additionally to public state.

The rest LGTM, ty!