binary(tests): vector cases for zero code chunks in the code zone

[awskii]

code_chunks_of_zero_bytes is 62 bytes of code, so both its chunks live in the
account header. Chunks past the header are keyed by code hash rather than by
address and are written on a separate path, and no vector pins that a zero chunk
is absent there too. A client can apply the rule in one zone and not the other
and still produce a root.

The second case adds the interaction with content addressing, which is also
unpinned: shared_bytecode_two_accounts and code_chunks_of_zero_bytes each hold
on their own, but nothing says what happens when the chunk two accounts would
share is the one that has to be absent.

Both cases are aimed at the code zone, so they survive the removal of code chunks
from the account header discussed in #3286 — the second becomes the central case
rather than an edge one, since every chunk would then be content-addressed.

Changes

• zero_code_chunk_in_the_code_zone — 160 chunks with an all-zero chunk at 130 in
  the code zone, and another at 5 in the header so a one-zone implementation is
  caught.
• shared_bytecode_with_a_zero_overflow_chunk — two accounts running that code:
  the zero code-zone chunk absent from the single leaf they would otherwise share.
• _zeroed_chunks helper, README case table, regenerated binary_trie_vectors.json.

Both roots are reproduced independently by erigon's EIP-8297 engine and by a
separate canonical-rebuild oracle in the same repo.

test_binary_tree_fork_matches_amsterdam_modulo_known_deltas fails on this branch
and on its base — unrelated fork.py drift from 42f26f1.

[kevaundray]

Apologies do you mind rebasing ser?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 21.91%. Comparing base (9b4db64) to head (3fb8497).
⚠️ Report is 14 commits behind head on projects/binary-trie.

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HEAD has 4 uploads less than BASE

Flag	BASE (9b4db64)	HEAD (3fb8497)
unittests	6	2

Additional details and impacted files

@@                    Coverage Diff                    @@
##           projects/binary-trie    #3305       +/-   ##
=========================================================
- Coverage                 93.00%   21.91%   -71.09%     
=========================================================
  Files                       628      628               
  Lines                     37395    37395               
  Branches                   3445     3445               
=========================================================
- Hits                      34779     8195    -26584     
- Misses                     1859    29115    +27256     
+ Partials                    757       85      -672     

Flag	Coverage Δ
unittests	21.91% <ø> (-71.09%)	⬇️

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