Test metrics from nightly builds

Goals:

• Get statistics of most flaky tests by re-running already passed integrations nightly
• Get statistics of which tests are being run and which are being skipped per branch (from the same nightly runs)
• Notice broken provisioning earlier (parallel builds)

Desired architecture

• nightly runs in coin on already integrated branch heads, results available publicly
• test result parser & db importer running outside of COIN
• new database with optimized data model
• Grafana (testresults) for viewing

Phases

1. Enable just for a QtBase branch
2. Enable for a whole Qt5 branch integration
3. Enable for multiple (2 or 3) branches
4. Separate nightly builds for provisioning