Modernization + AZStd::function compare fix. (#3680)

* Modernization + small fix.

Modernize ( `bool`/`override`/other) code in AzCore, AzFramework, AzQtComponents, AzToolsFramework, etc.
Replaced a `bind` or two, use `using` in a few places as well.

Fix nullptr comparison of AZStd::function.

Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com>

* Apply review-based changes

Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com>

Code/Framework/AzToolsFramework/Tests/Entity/EditorEntitySearchComponentTests.cpp

@@ -66,7 +66,7 @@ namespace AzToolsFramework
         {
         }
 
-        virtual ~EntitySearch_TestComponent1() override
+        ~EntitySearch_TestComponent1() override
         {}
 
     private:
@@ -123,7 +123,7 @@ namespace AzToolsFramework
         {
         }
 
-        virtual ~EntitySearch_TestComponent2() override
+        ~EntitySearch_TestComponent2() override
         {}
 
     private: