Optimize unicode string comparison with early length check

[Ameen-Alam]

Optimize unicode string comparison with early length check

Add a fast-path optimization to unicode_compare() that checks string lengths
before performing character-by-character comparison. When strings have
different lengths, we can return immediately since they cannot be equal.
This improves performance for the common case where strings of different
lengths are compared.

The change:

• Moves length checks to the start of the function
• Returns early if lengths differ
• Maintains existing comparison behavior
• Follows CPython coding style

[python-cla-bot]

The following commit authors need to sign the Contributor License Agreement:

• [email protected]

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[StanFromIreland]

Performance benchmarks?

[picnixz]

The change is also incorrect, as highlighted by the test failures. Please open an issue with results showing the improvements and the correctness.