Break apart monolithic TextStyle component

[alice-i-cecile]

This should probably be done in a future PR just to not let this one grow too much, but doing this for TextStyle should probably be done too.

Originally posted by @IceSentry in https://github.com/bevyengine/bevy/issues/5513#issuecomment-1200472999

Sibling to #5511, and should be done for the same reasons.

[Nilirad]

Pasting what I said in #5511:

Not sure if in-topic, but I think it would be good UX to have font weight/style and text decoration as their own components:

• Underline (as or with an enum with Normal, Dotted, Wavy, etc variants)
• Overline
• LineThrough
• Bold
• Italic