Add Python 3.14 Support

[lola831]

Description

This PR adds support for Python 3.14 in Scenic, including CI and dependency updates.

IMPORTANT: It is not ready to merge until pygame and python-fcl supports Python 3.14.

CI Support:

Added Python 3.14 to the GitHub Actions test matrix (run-tests.yml)
Enabled allow-prereleases: true to test against 3.14.0rc1

Tox support:

Extended tox.ini to include 3.14 environments
Worked around an issue where scenic[metadrive] was being installed even when python_version > 3.11 by listing metadrive-simulator directly with the correct version guard

Pre-commit updates:

Updated black and isort to run under Python 3.14

Sphinx compatibility:

Increased the upper bound for sphinx to <8 to allow versions compatible with Python 3.14
Patched object_description in conf.py to accept **kwargs (for compatibility with Sphinx ≥7.2 which passes a _seen kwarg) while remaining backward-compatible with older versions

Documentation:

Added a note in the simulator docs reminding users that not all simulators may support the same range of Python versions; users should verify support per simulator.

Issue Link

Checklist

• I have tested the changes locally via pytest and/or other means
• I have added or updated relevant documentation
• I have autoformatted the code with black and isort
• I have added test cases (if applicable)

Additional Notes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.18%. Comparing base (cf6bbfa) to head (1111842).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #371   +/-   ##
=======================================
  Coverage   91.18%   91.18%           
=======================================
  Files          54       54           
  Lines       13407    13409    +2     
=======================================
+ Hits        12225    12227    +2     
  Misses       1182     1182           

see 6 files with indirect coverage changes

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