[ecash-herald] Patch use of float vs int for sats

Summary: Oversight from implementation of staking rewards parsing. parseFloat will work fine but we should parseInt as all output.value instances from chronik are expected to be strings of satoshi values, i.e. integers.

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14791