shader: specialize cube image descriptors (#134)

* shader: specialize cube image descriptors

Track whether image descriptors refer to cube maps during resource specialization, and apply the coordinate offset conversion when sampling cube maps as 2D image arrays in SPIR-V emission.

* shader: fix cube array coordinate lowering

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Co-authored-by: nmzik <Nmzik@mail.ru>

src/graphics/shader/recompiler/ir/ShaderIR.h

@@ -432,6 +432,7 @@ struct MemoryInfo {
 	bool     typed           = false;
 	bool     formatted       = false;
 	bool     image_has_mip   = false;
+	bool     image_cube      = false;
 	bool     glc             = false;
 	bool     slc             = false;
 	bool     idxen           = false;
@@ -607,6 +608,7 @@ struct ImageResource {
 	bool                    written         = false;
 	bool                    atomic          = false;
 	bool                    depth_compare   = false;
+	bool                    cube            = false;
 
 	bool operator==(const ImageResource& other) const = default;
 };