frame_capture_utils.h is only used in tests so changing the name to be
frame_capture_test_utils.h is more appropriate. Also
frame_capture_utils.h will now be a file in libANGLE_with_capture
library where serialization code is stored.

Bug: angleproject:4806
Change-Id: I7482693a75b2d0edda7e84ae9b777fd3f46f1855
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2273917
Commit-Queue: Manh Nguyen <nguyenmh@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>