perf: deduplicate basic block operation batches in HasherOp replay

[berZKerk]

When recording replay data for Hasher chiplet trace generation, operation batches for basic blocks were cloned every time a block was entered, causing unnecessary duplication when the same basic block was entered multiple times.

This change introduces a BTreeMap<Word, Vec> to store each unique set of operation batches only once, keyed by the basic block digest.
The HasherOp enum now stores only the digest instead of the full batches, reducing memory usage and improving performance for programs with repeated basic block executions.

Fixes #2250

[huitseeker]

Consider adding tests that verify deduplication works when the same basic block is executed multiple times.

The existing tests pass, but none specifically check that op_batches_map deduplicates correctly. A simple test could record the same digest three times and verify the map has one entry while hasher_ops has three.

Example:

#[test]
fn test_hasher_request_replay_deduplicates_basic_blocks() {
    let mut replay = HasherRequestReplay::default();
    let digest: Word = [Felt::new(1), Felt::new(2), Felt::new(3), Felt::new(4)];
    let op_batches = vec![OpBatch::new(vec![Operation::Add], Vec::new()).unwrap()];

    replay.record_hash_basic_block(op_batches.clone(), digest);
    replay.record_hash_basic_block(op_batches.clone(), digest);
    replay.record_hash_basic_block(op_batches.clone(), digest);

    assert_eq!(replay.op_batches_map().len(), 1);

    let (hasher_ops, _) = replay.into_parts();
    assert_eq!(hasher_ops.len(), 3);
}

[huitseeker]

The comment says "we don't verify to avoid overhead", but a debug_assert_eq! would catch bugs during testing without runtime cost in release builds.

Consider:

alloc::collections::btree_map::Entry::Occupied(entry) => {
    debug_assert_eq!(
        entry.get(),
        &op_batches,
        "Same digest should always map to same op_batches"
    );
},

This guards against implementation bugs where different batches produce the same digest.

[huitseeker]

The impl IntoIterator for HasherRequestReplay still exists, but seems unused, now. It only returns hasher_ops and drops the op_batches_map. We should delete it to avoid confusion with into_parts.