Editor code: tidy up BOOLs,NULLs and overrides pt2.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 2 of a split #2847

Signed-off-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/Lib/Tests/test_Main.cpp

@@ -17,7 +17,7 @@ class EditorLibTestEnvironment
     : public AZ::Test::ITestEnvironment
 {
 public:
-    virtual ~EditorLibTestEnvironment() {}
+    ~EditorLibTestEnvironment() override {}
 
 protected:
     void SetupEnvironment() override