test/runner: Only run builds for relevant PR events
test/runner: Only run builds for relevant PR events

This change ensures that builds are only triggered by new pull
requests and pushes to open pull requests. Other events like
requesting a review, editing the description, and labeling should
not trigger a build.

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>

philiplb/flynn,philiplb/flynn,flynn/flynn,lmars/flynn,flynn/flynn,flynn/flynn,philiplb/flynn,lmars/flynn,philiplb/flynn,lmars/flynn,lmars/flynn,lmars/flynn,philiplb/flynn,flynn/flynn,flynn/flynn