[mock-chronik-client] Add tests to CI

Summary: Add mock-chronik-client unit tests to CI. We also want to run the CI tests for any apps that use this mock every time we see changes in this mock.

Test Plan: ./contrib/teamcity/build-configurations.py mock-chronik-client-tests

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15588