Have the test use the same clock (cputicks) as the profiler, and use the
test's own measurements as hard bounds on the magnitude to expect in the
profile.

Compare the depiction of two users of the same lock: one where the
critical section is fast, one where it is slow. Confirm that the profile
shows the slow critical section as a large source of delay (with #66999
fixed), rather than showing the fast critical section as a large
recipient of delay.

Previously reviewed as https://go.dev/cl/586237.

For #66999

Change-Id: Ic2d78cc29153d5322577d84abdc448e95ed8f594
Reviewed-on: https://go-review.googlesource.com/c/go/+/667616


LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Rhys Hiltner <rhys.hiltner@gmail.com>