runtime: hold sched.lock over globrunqputbatch in runqputbatch

runtime: hold sched.lock over globrunqputbatch in runqputbatch

globrunqputbatch should never be called without sched.lock held.
runqputbatch's documentation even says it may acquire sched.lock in
order to call it.

Fixes #40457.

Change-Id: I5421b64f1da3a6087dfebbef7203db0c95d213a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/245377
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>