Remove some testing-only image filter subclasses

The "fail" cases were all equivalent to ::Empty(). The identity case
is just a (0,0) offset. The "fixed-bounds" cases are handled with a
crop image filter and adjustments to the test arguments.

Bug: b/40040586
Change-Id: I9dd8d251b9a85313254cb81b2173fe78d9e2f34b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/743658
Auto-Submit: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed