feat: implement formal pytest plugin for test extras

[devin-ai-integration]

This PR targets the following PR:

• Feat: New CDK-Native FAST Standard tests, replaces CAT #349

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This PR implements a formal pytest plugin for the test extras in the airbyte-python-cdk repository. The plugin allows connector developers to easily use pre-built test suites without requiring test scaffold files.

Key changes:

• Enhanced the existing pytest plugin to add automatic test discovery capabilities
• Added pytest plugin entry points to pyproject.toml
• Created documentation in README.md explaining how to use the plugin
• Added unit and integration tests to verify the implementation

Link to Devin run: https://app.devin.ai/sessions/864fc782ea1b4e9c90d2fada1307ecfd
Requested by: Aaron ("AJ") Steers (aj@airbyte.io)

[devin-ai-integration]

Original prompt from Aaron:

In the Python CDK, we're adding new test "extra" that will have pre-built test suites that connector developers can easily use to run a full suite of tests. What benefits are there to making this a formal pytest plugin and what would that entail?


You only need to look in the following repo: airbytehq/airbyte-python-cdk

[devin-ai-integration]

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[devin-ai-integration]

Closing due to inactivity for more than 7 days.