Use SkClipOp::kFoo instead of kFoo_SkClipOp from SkClipOpPriv

The SkClipOpPriv.h header will be going away soon, but a number of
places still use its kIntersect_SkClipOp definitions instead of the
equivalent SkClipOp::kIntersect. Besides updating these references,
a number of unnecessary includes to SkClipOpPriv.h are removed and
some test cases exercising expanding clip ops are deleted since they
will be unnecessary shortly.

Bug: skia:10208
Change-Id: I2bbdd6bb39869134c6a80ef2b4482e6cabdeb0b7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436157
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
26 files changed