validationESEXT: Implement ValidateGetCompressedTexImageANGLE. Add CompressedTexImageNegativeAPI test. Bug: angleproject:6177 Test: angle_end2end_tests --gtest_filter="GetImageTest.CompressedTexImageNegativeAPI*" Change-Id: Ia7ed503a7a98f10e4b02deb3954f367f842da3fa Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3452112 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>