Changes to be back-ported from Amsterdam

[gurukamath]

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

• Implement state tracker in the older forks ( See feat(specs): Replace mutable State with PreState + StateTracker #2207)
  • Remove fork independent constants/functions/classes from fork_loader (See comment)
  • Add Amsterdam specific imports from the t8n tool to ForkLoader (See comment)
• Account dataclass should have code_hash instead of code (See feat(specs): Replace code with code_hash in Account #2244) (Closed in chore(spec): backport code_hash in Account change to previous forks #2345)
• Fork agnostic State - refactor(specs): make State fork agnostic #2381
• Update system contract access (See comment)
• Partially decouple state_transition from BlockChain (See feat(specs): Partially decouple state_transition from BlockChain #2307)
• Accept encoded LegacyTransaction (See feat: Accept RLP encoded legacy transactions in decode_transaction #2365)
• Delay get_code call (See refactor(specs): delay get_code calls in CALL-like opcodes after gas charging and stack-depth checks #2473)

[fselmo]

Going to put this one here as well #1867. I have an older version of this locally, will make sure to get this in.

I assume the state tracking and gas accounting may bleed together. Perhaps it may be good to wait for the state tracker to be fully implemented in forks/amsterdam to understand how these changes work together.