[Cashtab] Support slpv1 genesis txs for mint batons

Summary:
T3495

Enable creation of slpv1 tokens with a mint baton.

Support for minting txs will be added later.

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D15820