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/AzFramework/Tests/BehaviorEntityTests.cpp

@@ -29,7 +29,7 @@ public:
     void Activate() override {}
     void Deactivate() override {}
 
-    bool ReadInConfig(const AZ::ComponentConfig* baseConfig)
+    bool ReadInConfig(const AZ::ComponentConfig* baseConfig) override
     {
         if (auto config = azrtti_cast<const HatConfig*>(baseConfig))
         {
@@ -39,7 +39,7 @@ public:
         return false;
     }
 
-    bool WriteOutConfig(AZ::ComponentConfig* outBaseConfig) const
+    bool WriteOutConfig(AZ::ComponentConfig* outBaseConfig) const override
     {
         if (auto outConfig = azrtti_cast<HatConfig*>(outBaseConfig))
         {