Changes to be back-ported from Amsterdam

Sometimes, certain changes made to the Amsterdam fork need to be back-ported to older forks. However, doing this in one PR could blow up the size of the PR and make it unmanageable. This issues tracks such changes, that need a subsequent PR to back-port them to the older forks

- [x] Implement state tracker in the older forks
See ethereum/execution-specs#2207
Closed in ethereum/execution-specs#2750
- [x] Remove fork independent constants/functions/classes from `fork_loader` (See [comment](https://github.com/ethereum/execution-specs/pull/2267#discussion_r2836412797))
- [x] Add `Amsterdam` specific imports from the t8n tool to `ForkLoader` (See [comment](https://github.com/ethereum/execution-specs/pull/2207#discussion_r2816866110))
- [x] `Account` dataclass should have `code_hash` instead of `code`
See ethereum/execution-specs#2244
Closed in ethereum/execution-specs#2345
- [x] Fork agnostic `State`
See ethereum/execution-specs#2381
Closed in ethereum/execution-specs#2750
- [x] Update system contract access
See [comment](https://github.com/ethereum/execution-specs/pull/2264#discussion_r2835713125)
Closed in ethereum/execution-specs#2750
- [x] Partially decouple state_transition from BlockChain
See ethereum/execution-specs#2307
Closed in ethereum/execution-specs#2750)
- [ ] Accept encoded `LegacyTransaction` (See ethereum/execution-specs#2365)
- [x] Delay `get_code` call (See ethereum/execution-specs#2473). No need to back-port since it was undone in #2901
- [ ] Introduce gas meter dataclass (See ethereum/execution-specs#3159)
- [ ] Remove the `Message` dataclass (See ethereum/execution-specs#3192)
- [ ] Move static transaction checks from `check_transaction` to `validate_transaction` (See ethereum/execution-specs#3492)