[PATCH v4 0/4] MR5020: Draft: kernelbase/file: implement CopyFile2

[Kartavya Vashishtha (＠kvashis)]

copy implementation of CopyFileExW into CopyFile2,
then implement CopyFileExW in terms of CopyFile2

should fix https://bugs.winehq.org/show_bug.cgi?id=55897, as Python does not use any new functionality nor the callback parameter from CopyFile2.

- followed [the Wiki](https://wiki.winehq.org/Developer_Hints#Implementing_new_API_calls) for adding a new API call
- run `file.c` tests and they seem to pass

I have not written extensive documentation since the original function didn't seem to have any; I can do that if recommended.

I originally intended to implement the callback functionality in this MR as well, but realized that would be better as a follow-up.

--
  v4: CopyFile2_impl: remove unused variable

https://gitlab.winehq.org/wine/wine/-/merge_requests/5020