[Cashtab] Improve styles for button components

Summary:
Changes needed for implementing the new Collection component in D17074

They are general improvements though and can go here. Want to make sure buttons can display centered inline loaders while content is loading. And patch ts lint/props issue with CopyButton.

Since we are making improvements here and also incrementally converting Cashtab to ts, we also convert this to ts.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17096