Fix -Wnon-virtual-dtor in util and gtest wrapper

commit_hash:d8917bc04e6ab10b341000f8bb98d456223f0307

library/cpp/testing/unittest/gtest.h

@@ -33,6 +33,8 @@ namespace NTesting {
         inline TTest* _This() noexcept {
             return this;
         }
+
+        virtual ~TTest() = default;
     };
 }
 

util/ysaveload_ut.cpp

@@ -672,6 +672,7 @@ private:
         struct IInterface {
             virtual void Save(IOutputStream* out) const = 0;
             virtual void Load(IInputStream* in) = 0;
+            virtual ~IInterface() = default;
         };
         struct TBaseVirtual: IInterface {
             TString Str1;