refactor: split settings into smaller components

[setchy]

Split our growing Settings component into smaller, more focused components.

• Appearance Settings
• Notification Settings
• System Settings
• Settings Footer

[setchy]

I do wonder if these per-component test files are more effort than they're worth. Integration-level tests could cover all of these, pretty much, without needing to have a test-per. As it is, I feel that the tests make the system harder to change without contributing much resiliency to errors.

I would argue the opposite. They're easy to write and easy to make changes. I haven't had any concerns

[bmulholland]

Oh cool, good news!

[afonsojramos]

It would have been way easier to merge this after #1318 :(

[afonsojramos]

Nevermind, it was rather easy afterall 😁