2149: Handle IfLet in convert_to_guarded_return. r=matklad a=krk
Fixes https://github.com/rust-analyzer/rust-analyzer/issues/2124
I could not move the cursor position out of `let`:
`le<|>t` vs `let<|>`.
Also, please suggest extra test cases.
Co-authored-by: krk <keremkat@gmail.com>