[ecash-herald] Parse SwAP txs
Summary:
T3060
Parse SWaP txs
Handles some observed inconsistencies between spec and recent network txs (active apps appear to use ASCII for encoding / decoding sats). Stub parsing for uncommon methods, can be expanded as these txs are observed.
Test Plan: npm test
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Subscribers: Fabien
Differential Revision: https://reviews.bitcoinabc.org/D14054