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...)

Requires at least GCC 11, Clang 13, MSVC 19.30 (VS2022 17.0), or AppleClang 13.1.6 (XCode 13.3).

Qt Settings: Transfer OSD settings to a new OSD pane.

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

Change NAME to CONFIG_NAME while I'm at it.

dolphinQt: fix Qt6 deprecation warnings

Show "(off)" instead of "" when the default post-processing effect is
selected. This also indirectly fixes issues with keyboard navigation of
the post-processing effect combobox when the default is selected,
resolving https://bugs.dolphin-emu.org/issues/13863.

m_post_processing_effect was previously using the ConfigStringChoice
constructor that assumes the text and data of each option are identical.
This is true for all the other effects, but since "(off)" has the config
value of "" this assumption was failing for it, causing the combobox to
be blank.