Add tests for progressive containers and ProgressiveMerkleHasher

[eserilev]

Extend the differential property tests (#47) and derive macro tests (#48) to cover the new functionality in the progressive branch:

• Property test ProgressiveMerkleHasher against a recursive reference implementation of EIP-7916 merkleize_progressive, with random byte lengths and random write splits to exercise the partial-chunk carry buffer, up to 128 chunks to cross all early level boundaries.
• Property test ProgressiveBitList hashing against the same reference with independent bit packing, covering the empty-list workaround.
• Derive tests for progressive containers: skip_hashing interaction, nesting (both directions), generics, tree_hash_type, a six-field container crossing a progressive level boundary, and active_fields spanning multiple bytes.
• Hard-coded roots for the level-crossing and multi-byte cases computed independently from the EIP pseudocode, so these tests do not rely on the hasher under test.

Claude-Session: https://claude.ai/code/session_017PpXigbebk4GAQ9D9qdFzU

[eserilev]

@macladson was thinking of merging this into the progressive branch to add a bit more test coverage if that';s cool with you

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.77%. Comparing base (03d9fa4) to head (8674c20).

Additional details and impacted files

@@               Coverage Diff               @@
##           progressive      #50      +/-   ##
===============================================
+ Coverage        92.49%   93.77%   +1.28%     
===============================================
  Files                8        8              
  Lines              626      739     +113     
===============================================
+ Hits               579      693     +114     
+ Misses              47       46       -1     

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