Break apart monolithic `TextStyle` type

[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 #5513 (comment)

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

[rparrett]

I'm slightly confused by this issue -- I don't think TextStyle has ever been used as a Component and since #1245 (pre-this-issue) there's no way it really could be so I'm not sure how breaking it up would make things more ergonomic.

This could potentially become relevant again if "text sections as entities" gains traction in the future.

[alice-i-cecile]

Yeah, sorry about that, the wording was definitely misleading. I think that "text styles as entities" is still an interesting direction, but this isn't super actionable as is.