kernelbase: adding support for callback in CopyFileEx, and implementing CopyFile2

context: https://bugs.winehq.org/show_bug.cgi?id=55897

While implementing CopyFile2, I noticed that CopyFileEx does not respect the progress callback and never calls it. The tests too assume that it will not be invoked other than in the case of a file having multiple streams, which is not something that Wine supports.

There seem to have been multiple efforts to implement this functionality (in 2022 and 2013) but I can't tell find any reasoning for why they were not successful. Would implementing this be a desirable contribution?

I don't know how to get assigned to an issue on Bugzilla. I read the Wine Developers Wiki but it doesn't seem to have the information, so I left a comment in the bug log itself.