Audit winreg key queries before OS calls - #9593

Summary

• Emit CPython's winreg.QueryInfoKey and winreg.QueryValue audit events after argument conversion and before registry operations.
• For QueryValue, convert the required str | None subkey through UTF-16 before auditing and before the performance-data check, preserving lone surrogates and rejecting trailing or embedded NULs.
• Reconstruct the audit payload from UTF-16 as CPython does. Audit tuple/name objects are created only if audit hooks are active.

This does not address all winreg audit events or claim complete parity. Generic invalid-subkey type-error wording remains outside this change. The current-main reconciliation preserves the newer surrogate-safe PyStr return alongside the reviewed Wtf8Buf input and audit order. #9586 separately fixes the HKEY converter; #9589 addresses QueryValueEx.

Validation

• Independently source-reviewed against CPython v3.15.0 PC/winreg.c and its generated Clinic code, including event arguments and conversion order.
• prek hooks and git diff --check passed.
• The current-main conflict resolution passed independent source review, focused host-env/VM/stdlib Linux threading cargo check, normal all-targets Clippy, and ordinary hooks. Clippy diagnostics match four unchanged-main warnings; none were suppressed.
• These Linux checks do not type-check or execute the Windows-only registry code. Native RustPython execution and full workspace/C-API runtime suites were not run; hosted Windows CI remains required.