Does FSlateElementBatcher::AddCachedElements need to check if r.HDR.UI.CompositeMode is enabled?

When a specific configuration of HDR cvars are set, PIE in a New Editor Window will not render the game world.

Settings (For DefaultEngine.ini):
```
[SystemSettings]
r.AllowHDR=1
r.HDR.Display.ColorGamut=0
r.HDR.Display.OutputDevice=5
r.HDR.EnableHDROutput=1
r.HDR.UI.CompositeMode=0
Slate.EnableGlobalInvalidation=1
```

Also tested in //UE5/Main, CL: 35660734

The Licensee has suggested a fix for Mainline:

In the file ElementBatcher.cpp, and the function "FSlateElementBatcher::AddCachedElements(...)":
```
if (EnumHasAnyFlags(CachedBatch.GetDrawFlags(), ESlateBatchDrawFlag::HDR))

else

```

Note that in Unreal Engine 5.4, the function to modify is "FSlateBatchData::AddCachedBatchesToBatchData(...)" instead.

1. Download the Licensee's test project and open
Note that the Test project is built for //UE5/Main, but can be opened with //UE5/Release-5.4 with a new Level (see addl info URL)
2. Play PIE in "New Editor Window (PIE)" mode
3. Observe that the new PIE window does not render the game world, but still captures the mouse.