TextureCache: Don't re-use pooled textures within the same frame

This is an issue because a driver may have to maintain two copies of a
texture if it batches all uploads together at the start of a frame.

In the Vulkan backend, we do something similar to avoid breaking out of a
render pass to copy a texture from the streaming buffer to the destination
image.

This was causing issues in the sms-bubbles fifolog, where an EFB copy to
the same address of a previously-used texture caused the previous texture
to be re-used again for a different image later on in the frame, causing
the original contents to be discarded.

Source/Core/VideoCommon/TextureCacheBase.h

@@ -193,6 +193,7 @@ private:
   static void CheckTempSize(size_t required_size);
 
   static TCacheEntryBase* AllocateTexture(const TCacheEntryConfig& config);
+  static TexPool::iterator FindMatchingTextureFromPool(const TCacheEntryConfig& config);
   static TexCache::iterator GetTexCacheIter(TCacheEntryBase* entry);
 
   // Removes and unlinks texture from texture cache and returns it to the pool