ci: standardize CodeQL security analysis

[vgvoleg]

Use the common security-extended profile for Python and GitHub Actions with CodeQL v4. Run analysis on pull requests, supported-branch pushes, merge queues and weekly/manual triggers.

The SDK scan includes sync/async clients, examples, release scripts and package setup. Generated protobuf stubs and unit-test files are excluded.

Document the repository ruleset setting for requiring CodeQL results with a High/Critical security threshold before merge.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.68%. Comparing base (6a849d5) to head (0c21ddd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #916   +/-   ##
=======================================
  Coverage   82.67%   82.68%           
=======================================
  Files          99       99           
  Lines       12961    12961           
  Branches     1269     1269           
=======================================
+ Hits        10716    10717    +1     
+ Misses       1794     1793    -1     
  Partials      451      451           

Flag	Coverage Δ
integration	80.45% <ø> (+<0.01%)	⬆️
unit	49.21% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.
see 1 file with indirect coverage changes

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