runtime: move trace locks to the leaf of the lock graph

runtime: move trace locks to the leaf of the lock graph

Now that trace.lock cannot be held over a stack split, we can move
that lock and traceStackTab to the leaf of the lock graph. We add a
couple edges to STACKGROW that were previously passing through trace.

Fixes #53979.

Change-Id: Ie664ff7bb33973745f991f7516dc6106e60f5892
Reviewed-on: https://go-review.googlesource.com/c/go/+/418957
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>