Escape backslashes in generated docstrings

[Mirochill]

What does this PR do?

Fixes #3535.

Generated API docstrings can include literal backslashes from OpenAPI descriptions. When those backslashes are written directly into Python triple-quoted docstrings, Python 3.13+ can emit SyntaxWarning for invalid escape sequences such as \s.

This updates the generator docstring formatter so rendered backslashes are escaped for Python string literals, adds a formatter regression for a regex-style \s example, and updates the currently affected generated LogsPipelinesApi docstring.

Additional Notes

Not run locally.

Review checklist

Please check relevant items below:

• This PR includes all newly recorded cassettes for any modified tests.

• This PR does not rely on API client schema changes.

  • The CI should be fully passing.

• Or, this PR relies on API schema changes and this is a Draft PR to include tests for that new functionality.

  • Note: CI shouldn't be run on this Draft PR, as its expected to fail without the corresponding schema changes.

[github-actions]

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