Move functions testSchedLocalQueueLocal and testSchedLocalQueueSteal
from proc.go to export_test.go, the only site that they are used.

Fixes #14796

Change-Id: I16b6fa4a13835eab33f66a2c2e87a5f5c79b7bd3
Reviewed-on: https://go-review.googlesource.com/20640
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>