VideoBackends: Use VideoCommon shader generators for efb2tex copies.

This will generate one shader per copy format. For now, it is the same
shader with the colmat hard coded. So it should already improve the GPU
performance a bit, but a rewrite of the shader generator is suggested.

Half of the patch is done by linkmauve1:
VideoCommon: Reorganise the shader writes.

Source/Core/VideoCommon/TextureCacheBase.cpp

@@ -1997,7 +1997,8 @@ void TextureCacheBase::CopyRenderTargetToTexture(u32 dstAddr, EFBCopyFormat dstF
       entry->may_have_overlapping_textures = false;
       entry->is_custom_tex = false;
 
-      CopyEFBToCacheEntry(entry, is_depth_copy, srcRect, scaleByHalf, cbufid, colmat);
+      CopyEFBToCacheEntry(entry, is_depth_copy, srcRect, scaleByHalf, cbufid, colmat, dstFormat,
+                          isIntensity);
 
       u64 hash = entry->CalculateHash();
       entry->SetHashes(hash, hash);