runtime: fix a lock rank ordering and some edges.

The first stack-trace in #49361 shows that traceBuf must precede fin in
lockrank ordering, since traceBuf is acquired in StartTrace(), which
eventually leads to getting fin in queueFinalizer(). It is fine to move
traceBuf above fin, since there are no other conflicting dependencies.

The second stack trace shows that there is an edge bewtween reflectOffs
and fin, since reflectOffs is acquired in addReflectOff, and map
operations can lead to an allocation that eventually causes fin to be
acquired in queueFinalizer().

Fixes #49361

Change-Id: I8e857ef9ecdff37fdd229e4dba22e15bc71d4ba5
Reviewed-on: https://go-review.googlesource.com/c/go/+/361407


Trust: Dan Scales <danscales@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>