[Bug 46203] New: Renaming a file to a different capitalization of itself doesn't work

https://bugs.winehq.org/show_bug.cgi?id=46203

Bug ID: 46203
           Summary: Renaming a file to a different capitalization of
                    itself doesn't work
           Product: Wine
           Version: 3.21
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: kernel32
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 62878
  --> https://bugs.winehq.org/attachment.cgi?id=62878
Example fix + tests

Renaming a file in Wine to the same name but in different capitalization
doesn't work. For example, renaming "foobar" to "FooBar" doesn't work and is
basically a no-op. It works under Windows.

This is actually very annoying in practice when using file managers or file
browsers or anything else with Wine and trying to do that, so it's not just an
academic fix, but a practical one.

This should be special cased because now it finds that the target filename
already exists in the original case (which is good for other cases but not this
one) and thus uses that, effectively being a no-op.

Example patch + tests attached to fix this issue. It will probably need some
refinement, but it shouldn't break any current behavior except for fixing this
issue.