Rename batch->op in GrAuditTrail json and skiaserver's url handlers

Requires Infra change https://skia-review.googlesource.com/c/6397/

Change-Id: Ic04ea07a0450a99b291f1bc06d4a501d86f65f51
Reviewed-on: https://skia-review.googlesource.com/6398
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed