Before supporting EXT_clip_cull_distance extension,
some tests are added to validate the implementation
of EXT_clip_cull_distance extension. These tests are
implemented based on the tests for APPLE_clip_distance

Bug: angleproject:5458
Tests: angle_end2end_tests --gtest_filter=Clip*DistanceTest*
       angle_unittests --gtest_filter=*Clip*Distance*
Change-Id: I018c72ae8f0aff616c9d2600e63246e9609cf3de
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2585986
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>