[test] add a verbose logger to ChronikElectrumClient

Summary:
This will help troubleshoot test failures related to unexpected notifications and multiple clients.
The logger can use an optional name passed to the ChronikElectrumClient.__init__ method for easier debugging. By default this "name" is a unique number.

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18128