runtime: add lock partial order edge for trace and wbufSpans and mheap

runtime: add lock partial order edge for trace and wbufSpans and mheap

This edge represents the case of executing a write barrier under the
trace lock: we might use the wbufSpans lock to get a new trace buffer,
or mheap to allocate a totally new one.

Fixes #52794.

Change-Id: Ia1ac2c744b8284ae29f4745373df3f9675ab1168
Reviewed-on: https://go-review.googlesource.com/c/go/+/405476
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>