feat(tests): cover SYSTEM_ADDRESS accessed via delegation and withdrawal (EIP-7928)

[Sahil-4555]

What

Adds EIP-7928 block-access-list tests for SYSTEM_ADDRESS (0xff…fe) when it is genuinely accessed:

• test_block_access_lists_eip7702.py::test_bal_7702_delegation_to_system_address
• test_block_access_lists_eip4895.py::test_bal_withdrawal_to_system_address (zero and non-zero amount)

Why / flow

SYSTEM_ADDRESS is excluded from the BAL only as the synthetic caller of the block's system calls; once it is actually accessed it must be recorded like any other address. Two access paths were untested:

• 7702 delegation: a call to an EOA delegated to SYSTEM_ADDRESS loads the delegation target, so SYSTEM_ADDRESS must appear in the BAL.
• Withdrawal recipient: a withdrawal to SYSTEM_ADDRESS records the recipient regardless of amount, so SYSTEM_ADDRESS must appear in the BAL.

The existing eip7702 and eip4895 BAL tests never route an access through SYSTEM_ADDRESS, so neither path was covered. These were surfaced by cross-client differential testing - Erigon currently omits SYSTEM_ADDRESS from the BAL on both paths, so its BAL hash diverges from the other clients (reported to Erigon; Sepolia glamsterdam / 3.7.x, not mainnet). Adding the coverage here so the spec suite catches it.

Filling

Both fill and pass against the reference (EELS), which includes SYSTEM_ADDRESS in all cases:

tests/amsterdam/eip7928_block_level_access_lists/test_block_access_lists_eip4895.py .
tests/amsterdam/eip7928_block_level_access_lists/test_block_access_lists_eip7702.py .
6 passed

ruff check and ruff format clean.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.62%. Comparing base (faf6637) to head (b383366).
⚠️ Report is 18 commits behind head on forks/amsterdam.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           forks/amsterdam    #3681      +/-   ##
===================================================
+ Coverage            94.53%   94.62%   +0.08%     
===================================================
  Files                  624      624              
  Lines                37021    36976      -45     
  Branches              3349     3349              
===================================================
- Hits                 34999    34988      -11     
+ Misses                1429     1397      -32     
+ Partials               593      591       -2     

Flag	Coverage Δ
unittests	94.62% <ø> (+0.08%)	⬆️

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[fselmo]

Thanks! This adds some good cases. Just cleaned it up a bit 👍🏼