[CI] Add support for the ecash-coinselect lib on CI

Summary: Run the mocha tests for each diff touching a file from the lib folder, and report the test coverage.

Test Plan:

../contrib/teamcity/build-configurations.py ecash-coinselect

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14415