[Cashtab] Replace xecjs-message with bitcoinjs-message

Summary:
T3096

Depends on D13679

We should not maintain our own fork of bitcoinjs-message, as bitcoinjs-message already supports unique prefixes.

Drop in replace bitcoinjs-message.

Test Plan:
npm test
npm start
Sign a msg
Verify the msg
Verify it in ElectrumABC and confirm verified

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13694