Yellow squiggly lines begone!
Done automatically on .cpp files through `run-clang-tidy`, with manual corrections to the mistakes.
If an import is directly used, but is technically unnecessary since it's recursively imported by something else, it is *not* removed.
The tool doesn't touch .h files, so I did some of them by hand while fixing errors due to old recursive imports.
Not everything is removed, but the cleanup should be substantial enough.
Because this done on Linux, code that isn't used on it is mostly untouched.
(Hopefully no open PR is depending on these imports...)

VideoCommon: move global variables out of BPFunctions

VideoBackends / VideoCommon: add support for specifying include files in shader code

Make the function name more explicit and a better match for
GetDisplayName.

Change NAME to CONFIG_NAME while I'm at it.