enhancement: factor out a type from access lists

[richardgreg]

What was wrong?

Because it's repeated in several different transaction types, the Tuple[Address, Tuple[Bytes32, ...]] portion should be promoted to its own type.

Related to Issue # Fixes #947

How was it fixed?

This PR refactors the access list type used in various transaction classes to reduce redundancy and improve maintainability. Specifically, it introduces a new Access class to represent the access_list structure, which is used in multiple transaction types.

1. Created a new Access class to encapsulate the account and slots structure.

   @slotted_freezable
   @dataclass
   class Access:
   account: Address
   slots: Tuple[Bytes32, ...]

2. Updated Transaction Classes

3. RLP Encoding and Decoding Adjustments:

   • Introduced helper functions encode_access_list and decode_access_list to handle the conversion between the new Access type and the previous tuple structure for RLP encoding and decoding.
   • Updated encode_transaction and decode_transaction functions to use these helpers.

Cute Animal Picture

[SamWilsn]

This looks like pretty much exactly what I had in mind!

[richardgreg]

If this is good, I can do it for Prague if need be