address Damyan: specify constructors in interface, remove cleanup from interface

Author: bob80905

include/dxc/Support/dxcapi.extval.h

@@ -42,7 +42,7 @@ class DxcDllExtValidationLoader : public DllLoader {
 
   bool IsEnabled() const override { return DxCompilerSupport.IsEnabled(); }
 
-  void Cleanup() override {
+  void Cleanup() {
     DxilExtValSupport.Cleanup();
     DxCompilerSupport.Cleanup();
   }

include/dxc/Support/dxcapi.use.h

@@ -23,6 +23,9 @@ extern const char *kDxilLib;
 class DllLoader {
 public:
   virtual HRESULT OverrideDll(LPCSTR dll, LPCSTR entryPoint) = 0;
+  DllLoader() = default;
+  DllLoader(const DllLoader &) = delete;
+  DllLoader(DllLoader &&) = delete;
 
 protected:
   virtual HRESULT CreateInstanceImpl(REFCLSID clsid, REFIID riid,
@@ -55,7 +58,6 @@ class DllLoader {
 
   virtual bool IsEnabled() const = 0;
 
-  virtual void Cleanup() = 0;
   virtual HMODULE Detach() = 0;
 };
 
@@ -177,7 +179,7 @@ class SpecificDllLoader : public DllLoader {
     return true;
   }
 
-  void Cleanup() override {
+  void Cleanup() {
     if (m_dll != nullptr) {
       m_createFn = nullptr;
       m_createFn2 = nullptr;