perf: inline int.from_bytes in UUID conversion functions

[bdraco]

Summary

• Replace partial(int.from_bytes, byteorder="little") wrapper calls with direct int.from_bytes(..., byteorder="little") in _uint128_bytes_as_uuid, _uint16_bytes_as_uuid, and _uint32_bytes_as_uuid
• Remove the now-unused from_bytes_little definition from gap.py and its declaration from gap.pxd
• Eliminates ~0.025 us partial call overhead per LRU cache miss

Test plan

• All 73 existing tests pass
• Pre-commit hooks pass (ruff, mypy, codespell, etc.)

[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

---

_{Comparing optimize-uuid-inline-from-bytes (79b2465) with main (7a74ee9)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7a74ee9) to head (79b2465).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #202   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          255       254    -1     
  Branches        38        38           
=========================================
- Hits           255       254    -1     

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