feat: tx effects tree

[IlyasRidhuan]

Adds a tx effects unbalanced tree to the rollup, enabling more efficient proofs of tx effects.

Today, proving "tx X was included in this block and produced effects E" means replaying the whole checkpoint's blob sponge. With this root, it takes a single membership proof against one header field.

Summary

Structured leaf hash

• Each variable-length field of a TxEffect (note hashes, nullifiers, l2l1 msgs, public data writes, private logs, public logs, contract class logs) is hashed independently over that field's portion of the existing blob encoding.
• The tx start marker, transaction fee, and the seven field sub-hashes (from above) combine into a tx effect hash;
• This hash is combined with the tx hash to form the leaf (compute_tx_effect_leaf).

Wiring

• tx_base emits the leaf as TxRollupPublicInputs.tx_effects_tree_root
• tx_merge combines children via accumulate_tx_effects_tree_root
• block_root writes the result into BlockHeader.tx_effects_tree_root.
  Blob encoding refactor.
• The per-field blob-slice builders (create_public_data_writes_blob_fields, create_private_logs_blob_fields, create_contract_class_logs_blob_fields) are extracted out of tx_blob_data.nr so the same formats are used for the blob encoding and the new per-field hashes

Breaking / versioning

• BlockHeader and TxRollupPublicInputs both grow by one field (tx_effects_tree_root)
• Genesis header hash and archive root are recomputed (header serialization changed).
• ORACLE_VERSION_MAJOR 30 → 31 (noir-contracts and aztec-nr), TXE_ORACLE_VERSION_MAJOR 8 → 9.
• C++ world_state.cpp adds the matching zero field when hashing the initial (genesis) block header.