[Cashtab] [chronik tx history p10] Parse etokenAmount for token decimals

Summary:
T2447

Depends on D12129

Add support for parsing token decimals to parseChronikTx so that etokenAmount is correct for any given etoken

Test Plan:
Review new unit test + old mod and npm test
npm start and send or receive an etoken tx with multiple decimal places, review console.log output to confirm etokenAmount is correct for that tx

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D12130