Suppress Python 3.14 deprecation warnings for asyncio event loop policy APIs

[veeceey]

Summary

Fixes #3129

• sanic/server/loop.py: Added _get_event_loop_policy() and _set_event_loop_policy() wrapper functions that suppress the DeprecationWarning for asyncio.get_event_loop_policy and asyncio.set_event_loop_policy on Python 3.14+. These APIs still work but are deprecated and slated for removal in Python 3.16. The wrappers keep the same behavior while silencing the warnings.
• sanic/app.py: Replaced asyncio.get_event_loop_policy().get_event_loop() with asyncio.get_event_loop(), which is the direct equivalent and is not deprecated.
• bandit.baseline: Regenerated for bandit 1.9.x compatibility (the old baseline was generated with 1.8.6, causing security checks to fail for all PRs).

This addresses all three deprecation warnings reported in the issue:

1. asyncio.get_event_loop_policy in loop.py:46
2. asyncio.set_event_loop_policy in loop.py:47
3. asyncio.get_event_loop_policy().get_event_loop() in app.py

Test plan

• Verify no DeprecationWarning is emitted when running on Python 3.14 with uvloop
• Verify no DeprecationWarning is emitted when running on Python 3.14 without uvloop
• Verify existing test_server_loop.py tests still pass
• Verify behavior is unchanged on Python < 3.14

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.742%. Comparing base (785d77f) to head (94991da).

Files with missing lines	Patch %	Lines
sanic/server/loop.py	50.000%	7 Missing and 2 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3137       +/-   ##
=============================================
- Coverage   87.793%   87.742%   -0.052%     
=============================================
  Files          105       105               
  Lines         8143      8158       +15     
  Branches      1290      1292        +2     
=============================================
+ Hits          7149      7158        +9     
- Misses         687       692        +5     
- Partials       307       308        +1     

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