Fix: Handle Self replacement contextually in inline assists

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Only replace Self when inlining across different impl contexts, and use bare type names for expression contexts to avoid turbofish issues.

Fixes rust-lang/rust-analyzer#19827

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Thanks @Veykril for the feedback, I think it does make sense that we should leverage and extend the existing PathTransform mechanism that's already used for generic argument rewriting. I have updated the patch based on your review.