feat: add executeTransaction cheatcode

[onbjerg]

Summary

Adds a new executeTransaction(bytes calldata rawTx) cheatcode that executes an RLP-encoded signed transaction with full EVM semantics in an isolated context (similar to --isolate mode).

Ported from tempoxyz/tempo-foundry.

Interface

function executeTransaction(bytes calldata rawTx) external returns (bytes memory);

• Decodes EIP-2718 typed transactions (type prefix + RLP) or legacy RLP
• Recovers the signer from the transaction signature
• Executes in an isolated EVM: basefee/gas price zeroed, nonce checks enabled, EIP-3860 initcode limits enforced
• Merges state changes back into the parent context, preserving warm account/slot status
• Returns the execution output bytes
• Blocked in forge script contexts

Unsupported transaction types

OP deposit and Tempo AA transactions currently return an error with a TODO to add support later.

Test cases

• test_revert_not_a_tx — invalid RLP
• test_execute_legacy_transfer — type 0 ETH transfer
• test_execute_eip1559_transfer — type 2 ETH transfer
• test_execute_erc20_transfer — contract interaction (approve + transferFrom)
• test_execute_then_interact — state isolation: prank call after executeTransaction

Files changed

• crates/cheatcodes/spec/src/vm.rs — cheatcode declaration
• crates/cheatcodes/Cargo.toml — added foundry-primitives dep
• crates/cheatcodes/src/evm.rs — implementation
• testdata/utils/Vm.sol — auto-regenerated
• testdata/default/cheats/ExecuteTransaction.t.sol — tests