[WiP][JENKINS-19154] Publish test results in real time

[JENKINS-19154](https://issues.jenkins-ci.org/browse/JENKINS-19154)
A draft to support discussion at [dev-list](https://groups.google.com/forum/?fromgroups#!msg/jenkinsci-dev/M9pt1vvdrCo/aFPQkMj2KIUJ)