AbstractPipeline: Support returning "cache data"

"Cache data" can be used to assist a driver with creating pipelines by
using previously-compiled shader ISA.

Source/Core/VideoBackends/D3D12/Renderer.h

@@ -41,7 +41,9 @@ public:
                                                          size_t length) override;
   std::unique_ptr<NativeVertexFormat>
   CreateNativeVertexFormat(const PortableVertexDeclaration& vtx_decl) override;
-  std::unique_ptr<AbstractPipeline> CreatePipeline(const AbstractPipelineConfig& config) override;
+  std::unique_ptr<AbstractPipeline> CreatePipeline(const AbstractPipelineConfig& config,
+                                                   const void* cache_data = nullptr,
+                                                   size_t cache_data_length = 0) override;
 
   u16 BBoxRead(int index) override;
   void BBoxWrite(int index, u16 value) override;