Official support for Python 3.14

[sentrivana]

Problem Statement

Python 3.14 was released on Oct 7.

Solution Brainstorm

We need to:

• run the common test suite on 3.14
• fix any issues
• ideally, also do some manual testing
• if everything looks good, add 3.14 to classifiers
• once 3.14 is in classifiers, rerun scripts/generate-test-files.sh to update the integration test matrix with 3.14 as well where applicable

[linear]

PY-1876