[Cashtab] Convert Send screen and some deps to ts

Summary: As prep for adding bip21 token send support, convert Send screen to ts. Also convert opreturn methods to ts as they are used in this screen.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D17207