3285: Handle trivia in Structural Search and Replace r=matklad a=adamrk
Addresses the second point of https://github.com/rust-analyzer/rust-analyzer/issues/3186.
Structural search and replace will now match code that has varies from the pattern in whitespace or comments.
One issue is that it's not clear where comments in the matched code should go in the replacement. With this change they're just tacked on at the end, which can cause some unexpected moving of comments (see the last test example).
Co-authored-by: adamrk <ark.email@gmail.com>
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