[CI] Push coverage data to Teamcity statistics

Summary:
This will allow for graphing the coverage values and trigger events on
thresholds.

Test Plan:

../contrib/teamcity/build-configurations.py build-coverage

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7211