[Cashtab] Trim address strings in multisend input

Summary:
Currently, Cashtab will not tolerate any extra spaces around address strings in multisend input. Easy to support these with trim(), but need to also trim() where they are implemented

Note that the generateTxOutput is slated for deprecation when src/transactions version of sendXec function is implemented

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14987