There was a lot of locale handling to get correct/expected date
formatting within the app.
Carbon now has built-in locale content rather than us needing to target
specific system locales.
This also removes setting locale via Carbon directly.
Carbon registers its own Laravel service provider which seems to
accurately pull the correct locale from the app.
For #4555
- Reduced app settings down to what's required.
- Used new view-shared $locale object instead of using globals via
config.
- Aligned language used to default on "locale" instead of mixing
locale/language.
For #4501
