Fix Foundry blockhash handling and clear compiler cache in CI

[MontrealAI]

Motivation

• Foundry fuzz tests were failing because vm.setBlockhash was being called for blocks in the future, producing "block number must be less than or equal to the current block number" errors.
• CI surfaced warnings from unsupported forge_version keys in foundry.toml that should not be declared in profiles.
• A foundry_compilers::cache deserialization error suggested a stale/corrupted incremental compiler cache file was being restored in CI.
• Test invocation snippets referenced non-portable paths (e.g., /root/.foundry/bin) that break in different runner/home environments.

Description

• Added _rollPastAndSetBlockhash(uint256, bytes32) helper to test/v2/ValidatorStakeLock.t.sol and replaced the direct vm.setBlockhash call so the test always rolls past the target block before setting the blockhash.
• Removed forge_version entries from foundry.toml to eliminate the Foundry profile warnings.
• Added rm -f cache/solidity-files-cache.json || true steps to the Foundry CI jobs (.github/workflows/ci.yml, contracts.yml, and fuzz.yml) so stale compiler cache files are removed before running forge test.
• Kept the prior CI refactor intact and avoided changing unrelated test runners or Python/torch defaults.

Testing

• No automated tests were executed within this workspace as part of the change; CI will run the existing Foundry jobs to verify behavior.
• Recommended local verification commands are forge test --match-path test/v2/ValidatorStakeLock.t.sol -vvvv and forge test -vvvv --ffi --fuzz-runs 256 --match-contract 'CommitReveal|Stake|Fee|Slashing'.
• The three previously failing tests (testSlashingSucceedsWithShortUnbondingPeriod, testValidatorCannotFinalizeWithdrawalWhileAssigned, and testValidatorWithdrawStakeRevertsDuringActiveJob) are expected to pass when running the above Foundry commands.
• After these changes CI Foundry jobs should be quieter and avoid the foundry_compilers::cache deserialization noise once workflows run on the branch.

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Codex Task