settings_common: Remove unused optional

Reduces some ugliness in frontend code.

Suggests to a frontend how to represent each setting.

This gets rid of some repeated code and sets us up to send more
information to the new widget.

Currently unused, but I don't want to start headaches when someone
decides to use it the first time.

Renames enum values to conform to naming convention.

The new enum macros don't support setting values directly.
For LastAA and LastFilter, this means we need a simpler approach to loop
around the toggle in the frontend...

This lets us define an enum and all the textual representations
of its values in one swing. All for the price of some ugly macros.

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.