Revert "[Cashtab] Convert wallet context to ts"

Summary:
This diff broke prod so needs to be backed out immediately. Will figure it out later.

This reverts commit d425432410004f769719205bed6f2429d5b8b1a5.

Test Plan: npm test

Reviewers: #bitcoin_abc, johnkuney

Reviewed By: #bitcoin_abc, johnkuney

Differential Revision: https://reviews.bitcoinabc.org/D17297