Add `showSyntaxErrors` extension setting (#504)
## Summary
This PR adds a `ruff.showSyntaxErrors` config option for
https://github.com/astral-sh/ruff/pull/12059.
## Test Plan
Refer to the test plan in https://github.com/astral-sh/ruff/pull/12059.
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Co-authored-by: Micha Reiser <micha@reiser.io>
