Fix binding dummy textures for augmented shaders

The dummy textures supposed to be used when the shader declares a
texture, but has no binding, doesn't work correctly. The implementation
build a samplerBindingsSpecified bit array but never used it.

Read the combined samplers from the fragment shader and track the
sampler bindings as they are applied, and bind dummy textures and
samplers to those that were not specified.

Also fixes depthTextureArrayBinding using the wrong depthTextureBinding
variable, which is -1 when the array binding is used.

Also adds missing 2D array and Cube array sampler types. The cube map
arrays are not supported by rhi so modified the dummyTexture to return
plain cube map.

Also fixed filling all cube map faces and the same loop in custom
materials.

Also added a test for this case.

Pick-to: 6.12 6.11
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Change-Id: Iea3c876365da3fb8228b0e7c0347e559a45cd277
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>