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...)

Remove window hints clearing the flag Qt::WindowContextHelpButtonHint,
which is already off by default in Qt 6.

In Qt 5 this flag was set by default for QDialogs, and on Windows put a
? button in the corner of the title bar allowing users to activate Qt's
QWhatsThis help system for a given widget. Since we don't set that text
the ? button was useless and so we hid it manually.

to eliminate redundant unused members in Wii Remote extension objects.

WiiTASInputWindow: Update controls when attachment changes

Change the displayed controls in the TAS Input window when the
controller's extension (including MotionPlus) is changed.

This previously required restarting Dolphin after the attachment was
changed, as the controls were never updated after the WiiTASInputWindow
was created at Dolphin startup.

This apparently didn't compile on macOS six years ago before c++20, but
it should be fine by now.

While I'm at it, make the constants upper case per convention.