move Sk{Test,Random}ScalerContext to tools

There's no need for Skia users to link this test code.

Change-Id: I9d6ef2a053d0cf5cb916aa254389ca819c48bae1
Reviewed-on: https://skia-review.googlesource.com/69922
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
9 files changed