Check for astc_sliced_3d extension in negative API tests

Check for astc_sliced_3d extension in negative API tests

The ASTC sliced_3d extension allows support of 3D ASTC textures using 2D
blocks (interpreted as XxYx1 blocks of the 3D texture). That makes
passing the 2D ASTC format enums with a texture target of TEXTURE_3D
legal, so update the negative API tests to allow that case.

Components: OpenGL
VK-GL-CTS issue: 2741
Affects: dEQP-GLES3.functional.negative_api.texture.compressedteximage3d_invalid_astc_target
         dEQP-GLES3.functional.negative_api.texture.texstorage3d_invalid_astc_target

Change-Id: Ifd3c54d2819d11c3e771ad4a98682e266c27da41
(cherry picked from commit 6c72e55e2343f0b448c0707d0ae6b51f2baa3e61)