[Cashtab] Support min fee sends for holders of 1000 Cachet

Summary:
Implement first feature unlock for Cachet holders by enabling the 1.0 sat/byte fee setting for holders of 1000 Cachet

Note: While it is cumbersome to always be checking now for both Grumpy and Cachet, I do not think it is worth combining these checks into one function. As Cashtab evolves, I would like to retain control over specific features for specific tokens.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D16057