Cleanup some stuff found by MSVC's /analyze

* Added some missing `noexcept`s on custom destructors.
* Fixed `std::move` being called on a const-reference.
* Initialized `ScopedMessage::m_moved` in class definition, instead
of doing so in constructors explicitly.
* Turned some `enum`s into `enum class`es.
* Initialized `StreamingReporterBase::currentTestCaseInfo` in class
definition.
* Some cleanups in SelfTest code.

tests/SelfTest/UsageTests/Tricky.tests.cpp

@@ -185,7 +185,7 @@ struct Obj
 {
     Obj():prop(&p){}
 
-    int p;
+    int p = 0;
     int* prop;
 };