[Cashtab] Migrate Airdrop component tests to ts

Summary:
Continue Cashtab test migration from js to ts.

In this migration, we discover that the tokenMocks param of the helper function prepareMocks is not configured to accept custom tokens that a test may need. We make this adjustment to support this (and future) conversions.

We also make other type-related corrections to mocks that were related to this test (expected benefit of continued typescript conversion).

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D18341