[`pylint`] Detect `pathlib.Path.open` calls in `unspecified-encoding` (`PLW1514`) (#11288)
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## Summary
Resolves #11263
Detect `pathlib.Path.open` calls which do not specify a file encoding.
## Test Plan
Test cases added to fixture.
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Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>