[Cashtab] Add Collection component to better organize and render NFTs

Summary:
The NFTs page is becoming unusable due to slow load times. We need a more attractive and efficient component to render listed NFTs in a Collection.

Introduce the tested Collection component.

Test Plan:
npm test

This diff is live at prod testing site
Can see the updated NFTs screen featuring this component at https://cashtab-local-dev.netlify.app/#/nfts

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D17074