vrend: Fix more texture issues
- Add swizzles for incomplete vec4 texture buffer reads
- Fix layers with texture views.
Fixes CTS:
KHR-GL43.shader_image_load_store.advanced-sync-imageAccess
KHR-GL43.texture_view.view_sampling
Also GravityMark now looks okay, only the asteroid locations seem different.
Edited by Gert Wollny