eiffel: Switch build job triggers to GitHub trigger

eiffel: Switch build job triggers to GitHub trigger

The jobs were created to run periodically to settle the basics and
gather feedback from the projects.

ETOS project prefers the builds to be run upon merge of the commits
and this seems to be useful for other projects as well so the jobs
are modified to run based on GitHub triggers.

Jobs are renamed to reflect the fact as well.

Next change in the series enables posting comments back to PR if the
job is triggered due to merge of a PR.

Change-Id: I59a32c567def96550ee2297a985694f894339a85