Migrated ITestCase to std::shared_ptr

include/internal/catch_interfaces_testcase.h

@@ -16,12 +16,13 @@ namespace Catch {
 
     class TestSpec;
 
-    struct ITestCase : IShared {
+    struct ITestCase {
         virtual void invoke () const = 0;
-    protected:
         virtual ~ITestCase();
     };
 
+    using ITestCasePtr = std::shared_ptr<ITestCase>;
+
     class TestCase;
     struct IConfig;