Match SQLite callback keyword parsing - #9737

Summary

Retire the remaining expected failures in test_sqlite3/test_userfunctions.py and test_sqlite3/test_hooks.py as one file-level batch.

SQLite's defining-class Clinic wrappers use _PyArg_UnpackKeywords, even when every argument is positional-only. The generic native calling convention previously rejected keywords before that parser could report a missing positional argument or an excess total argument count.

• Add a typed UnpackKeywords<T> adapter. Its FORCE_UNPACK_KEYWORDS compile-time metadata selects CPython's _PyArg_UnpackKeywords calling and validation conventions through the existing binder, preserving argument conversion and displayed signatures. Positional-only parameters still cannot be passed by keyword.
• Keep default binding behavior and its successful-call fast path unchanged. Opaque or malformed argument shapes cannot use the adapter.
• Apply the same convention to aggregate, collation, window-function, authorizer, and trace callback registration.
• Remove only the three obsolete expected-failure decorators through scripts/update_lib; existing skips, assertions, test logic, and data are unchanged.
• Add shared-binder coverage for scalar, receiver, and flattened forms, and compile-time dispatch/signature coverage. No duplicate Python snippets.

This is independent of the other open expected-failure batches and is based directly on main ea5fbcc00.

Reference: CPython 3.15 SQLite generated wrappers and _PyArg_UnpackKeywords.

Validation

Behavioral validation before the identifier/documentation-only rename (binding and conversion logic unchanged):

• SQLite-enabled threaded release build passed.
• The two complete target modules passed: 106 tests, five existing skips, zero remaining expected failures.
• Full SQLite, builtin, call, inspect, and descriptor regression modules passed: 1,407 tests, 271 existing skips, four unrelated expected failures.
• 212 focused binding checks, five text signatures, and a control for ordinary positional-only dispatch passed.
• Strict workspace all-target Clippy, including SQLite, passed with -D warnings.
• Formatting, diff checks, normal commit hooks, and independent source review passed.

Before the naming-only revision, workspace tests passed: 1,520 passed, zero failed, 20 ignored across unit, integration, and doc tests. Separate C-API tests passed: 149 passed, zero failed, two ignored, and separate C-API all-target Clippy passed with -D warnings.

On naming revision 1a834ea436, normal commit hooks, formatting, diff checks, and strict workspace all-target Clippy including SQLite have passed again. Workspace tests and separate C-API checks are still running; earlier interrupted compilations are not counted as passing.

CPython 3.15 behavior is checked against the fixed source above; no CPython 3.15 runtime oracle is claimed. A clean merge was verified against current main 9670d1b364, including the subsequent #9706, #9668, and #9718 changes. No unrelated module expansion is included.

Normal hosted CI is enabled. Full hosted and cross-platform validation remains outstanding; this is not a merge-ready claim.

AI assistance: OpenAI Codex assisted implementation, source review, and validation. The model version is not exposed. Commits include Assisted-by trailers.