refactor(deep_branch_testing): use CREATE2 address derivation and fix gas

Major refactor of the depth benchmark test for execute mode:

- Remove stubs dependency; derive contract addresses directly from
  init_code_hash + Nick's deployer using CREATE2 formula
- Deploy AttackOrchestrator and Verifier as part of test execution
- Dynamically compute NUM_CONTRACTS based on gas_benchmark_value
- Add verification transaction at end of block to confirm attack success
- Fix gas constants based on empirical measurements:
  - GAS_PER_ATTACK: 8014 -> 8050 (measured ~8042)
  - MAX_ATTACKS_PER_TX: 1990 -> 1980 (safety margin)
  - TX_OVERHEAD: 22900 -> 22600 (more accurate)

The previous gas constants caused all attack transactions to run out
of gas, as the 28 gas/attack shortfall compounded over 1990 attacks
to ~55k gas deficit.

Author: CPerezz