GL_OES_texture_cube_map_array is core in 3.2. This CL adds support
for this extension in the shader translator.
Now passes dEQP.KHR_GLES31/core_texture_cube_map_array.*,
dEQP.GLES31/functional_fbo_color_texcubearray_*, and
dEQP.GLES31/functional_opaque_type_indexing*samplercubearray* with GL backend.

Bug: angleproject:3584
Change-Id: I1a8485c7d9d3fffb9b5109d292b35b0c56a3c665
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2133086Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>