Clang versions < 15 have compile issues with explicit instantiation.
Disable it for these versions.

Fixes -Wshadow, -Wdeprecated, and catch by copy rather than by ref.

Reduces branching/swictch cases for simplicity/code size

Reduces some confusion hopefully, since some parameters specified were not
specific to the setting in question.

The shorter constructor enables us to specify some options without needing to
specify the default values of multiplier which wasn't always appropriate and
could be confusing.

Almost a 2 year old migration setting now

Reduces the need for the compiler to duplicate this code, by about
100KB executable size.

ToString didn't have a constexpr if statement where needed.
Canonicalize missed an else, causing unreachable code error on MSVC.

Reduces compile times a tad on clang.

This particular setVisible function is unnecessary.
It also has horrible runtime performance, so much that it consumed maybe
80% of the time used to create a widget.

ConfigurationShared::Widget needs to be created with a builder. This
would avoid some duplicated code.

Using typeid without including typeinfo first produces an ill-formed program.

Clicking the slider without directly interacting with the slider handle would
change the value, but not trigger the restore button.

Explain why we need to do things differently at times, to serve as a
reference.

Groups graphics audio and system settings together in a way that
reflects the frontend. This also just conceptually groups them more
nicely than they were.

Also adds a couple characters that denotes the state of the setting.
M for modified, or not default.
C for custom, in context of per-game settings.

Gives every option of the enums a string literal via a macro.