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/D3DCommon/Shader.cpp

@@ -23,11 +23,6 @@ Shader::Shader(ShaderStage stage, BinaryData bytecode)
 
 Shader::~Shader() = default;
 
-bool Shader::HasBinary() const
-{
-  return true;
-}
-
 AbstractShader::BinaryData Shader::GetBinary() const
 {
   return m_bytecode;

Source/Core/VideoBackends/D3DCommon/Shader.h

@@ -16,7 +16,6 @@ public:
 
   const BinaryData& GetByteCode() const { return m_bytecode; }
 
-  bool HasBinary() const override;
   BinaryData GetBinary() const override;
 
   static bool CompileShader(D3D_FEATURE_LEVEL feature_level, BinaryData* out_bytecode,