runtime/trace: record HeapGoal when StartTrace

runtime/trace: record HeapGoal when StartTrace

Fixes #52517

Change-Id: I06aa6112f14f264360c3bb0ffd4e1cd54ad22514
Reviewed-on: https://go-review.googlesource.com/c/go/+/401777
Reviewed-by: hopehook <hopehook@golangcn.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>