Stop tracking total method execution time per transaction

Since method timings are inclusive the total method execution time per request is almost always greater than the total transaction time, thus confusing users and being fairly useless in general. This should be removed.

mentioned in commit 945c5b3f

mentioned in merge request !4124 (merged)

Status changed to closed by commit 945c5b3f

mentioned in commit 5298c3cc

Mentioned in commit pfjason/gitlab-ce@945c5b3f

mentioned in commit test-nick/gitlab-ce@f30170b6