arb_clear_texture: Test glClearTexImage and depth only textures
Test glClearTexImage in the same tests we test glClearTexSubImage for a better coverage.
Add tests of glClearTex(Sub)Image for depth only textures.
This reproduces a crash in iris:
../src/intel/blorp/blorp_genX_exec.h:1554: blorp_emit_surface_states: Assertion `params->depth.enabled || params->stencil.enabled' failed.
in arb_clear_texture-depth
.