refactor(txe): pass GasSettings as a struct to oracles

[nchamo]

Stacked on #25169, which re-expressed TXE-only oracle wire types as STRUCT/OPTION compositions instead of opaque LEAF mappings. This does the same for GasSettings.

The change

Three TXE oracles (private_call_new_flow, public_call_new_flow, set_private_txe_context) took [Field; GAS_SETTINGS_LENGTH], produced by calling gas_settings.serialize() at the call site. They now take GasSettings directly, and the TypeScript side describes it as a STRUCT of Gas/GasFees components, so the wire shape comes from the type mapping rather than from a hand-written serialization step.

The mapping is typed to a plain wire type (GasSettingsData) rather than to the GasSettings class, following the noir-structs/ convention already used in PXE: a type mapping describes the wire, and constructing the domain object is the consumer's job. The GasSettings.from(...) conversion happens in the three TXESessionStateHandler methods, the same way notifyCreatedContractClassLog converts its own wire type.

Because the mapping is now purely structural, private_call_new_flow_oracle and public_call_new_flow_oracle come off the #[generate_oracle_tests_excluding] list, taking the generated serialization suite from 95 to 99 tests. set_private_txe_context_oracle stays excluded on its PrivateContextInputs return, which is a separate follow-up.

This is a breaking oracle wire change (eight separate scalar slots instead of one eight-field slot), so TXE_ORACLE_VERSION_MAJOR goes 4 → 5.

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 1 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/1bcda4a1be7ec5cb�1bcda4a1be7ec5cb8;;�): yarn-project/kv-store/scripts/run_test.sh src/sqlite-opfs/internal/ordered-binary-browser.test.ts (2s) (code: 0)