[ty] inlay hint keyword arg edit (#24667)
Closes https://github.com/astral-sh/ty/issues/3281
## Summary
Implements the "click to add keyword argument": call argument name inlay
hints now carry `textEdits` so clicking one inserts the keyword name
into the source (e.g. `foo(1)` to `foo(x=1)`).
## Test Plan
Unit tests, e2e tests, manual testing
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Co-authored-by: Micha Reiser <micha@reiser.io>
