Add fixtures cache and Telescope picker for ambiguous fixtures

[Nosterx]

This pull request introduces the following changes:

Fixture Caching:

• Adds a cache for fixture information to avoid delays on the pytest --fixture -v command, which can take several seconds (up to six seconds in my experience) in large codebases.
• Implements autocmd to populate the cache automatically when Python test files are entered, written, or read.

Handling Ambiguous Fixtures:

• When multiple fixtures with the same name are defined in different locations, opens a Telescope file chooser with preview to allow the user to select the desired file.
• According to pytest-dev/pytest#3966, resolving the correct fixture location is challenging even for pytest itself.

[arturbalabanov]

Just discovered this plugin (awesome work @AckslD!) and ran into the same annoyance. Was going to implement caching and then saw this PR -- works great, thank you @Nosterx!

[AckslD]

Maybe this could at least be opt-out? Same as the commands above

[Nosterx]

Thanks for the suggestion! I've added a configuration option to enable/disable the auto-commands feature. If auto-commands are disabled, the fixture cache will still be populated when the to_declaration method is called. Let me know if you have any further feedback! 😊

[AckslD]

@Nosterx! This looks great, nice work! Also thanks for submitting a clean PR :) I just have one question above, otherwise happy to merge.