MergeService#merge has no timeout and can hang forever
From https://gitlab.com/gitlab-org/gitlab-ce/issues/53228, we saw that a MergeWorker
has no timeout and can therefore get stuck unless the RSS killer happens to come along and kill it. We can see this in the max timeout of the jobs in the last 7 days:
I think we want some timeout--not sure what the right value would be.