Rename GrTestBatch and subclasses to Op

Change-Id: Ideab66b7ca227057a767be48aba3ea69a0a19115
Reviewed-on: https://skia-review.googlesource.com/6161
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed