[Cashtab] Convert agora tests to ts

Summary:
Want to standardize all of Cashtab tests. Use ts and standardized test helpers.

Note: this is almost entirely AI-generated (cursor)

imo this is one of the areas it is best at, large scale refactor that is mostly type checking across lots of mocks, the kind of tedious improvement that risks otherwise being postponed indefinitely.

That said, still saw some weird behavior, like some outputScripts in mocks changed. Still does need to be reviewed. But changing only the test files and getting the same behavior but with typescript is imo a win.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D18322