Update SA1649CodeFixProvider to fix problems related to linked files #3862
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Fixes #1693 and #3866.
Unsure how to unit test this properly, but I have also used the code fix "live" in this repository with good success:
https://github.com/bjornhellander/SA1649CodeFixProblem
Shared Projects still doesn't work, with exceptions being thrown and the fix messing up the projects, but it does not seem to behave worse than before. (The built-in rename refactoring MoveTypeCodeRefactoringProvider also throws exception on this, but handles files and projects better.) But normal linked files between projects seem to be handled correctly with these changes.
I have started looking at the new APIs to rename files, but since these issues seems to be solvable without them I didn't add those part in this PR.