SA1412 code fix does not work properly on linked files

[sharwell]

When the SA1412 code fix is applied to a fix that is included in the project via a link, a copy of the original file is made at the target location of the link, and the new copy is included in the project instead of the original file.

💭 It might be possible to trick this into working by using a normal code fix that inserts a blank line at the beginning of the document. This would trigger a violation of a different rule, but then by fixing all instances of that rule you'd have a working encoding change that doesn't require changes to the project system.

[pdelvo]

I dont think this would work. I tried to make a text change to the document so that the encoding change is not the only change. but the encoding change was not working.

[sharwell]

Blocked on dotnet/roslyn#4767