feat: add #[serde(default)] to accessList field in TxEip4844

[davidp94]

Motivation

When deserializing EIP-4844 transactions, the accessList field may be missing from some sources or networks. Without a default, deserialization fails if the field is absent, even though an empty access list is a valid default per the spec. This causes compatibility issues, especially when working with networks or tooling that omit this field.

Solution

This PR adds #[serde(default)] to the accessList field in the TxEip4844 struct. This ensures that if the field is missing during deserialization, it will default to an empty access list, improving compatibility and robustness. No breaking changes are introduced, and this aligns with how similar fields are handled in other transaction types.

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PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

does missing mean null or actually missing?

do you have reference data for this that we can add as test?