runtime: move traceStackTable.lock to the system stack
runtime: move traceStackTable.lock to the system stack

This lock is acquired under trace.lock, which as of CL 418956
(6c2e327e35b) must be acquired on the system stack, so this lock must
be, too.

Fixes #54553.

Change-Id: I4fb0c0c2dfc3cb94b76673e842ad416305a31238
Reviewed-on: https://go-review.googlesource.com/c/go/+/425097
Reviewed-by: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Run-TryBot: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
Reviewed-by: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go