Make the CI record and track the unit tests
This prevents running the tests in parallel but make the CI report
useful info in case of failure and allow for tracking the flaky tests.
See result on CI.
Running the build-diff configuration should create 2 different junit files, with different test suite names.
In the CI UI, the Tests tab should display each test case individually, associated with its test suite.
Reviewers: #bitcoin_abc, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, deadalnix, jasonbcox
Subscribers: markblundeberg, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D5042