Small Code/Editor cleanup pass (#4909)

* Clean-up in ConfigGroup

Removed unused templated AddVar and related code.
Replaced legacy types with `AZ::` ones.
Cleaned up cpp file.

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

* Add a few missing Q_OBJECT macros, remove some unused variables.

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

* Apply some of clazy suggestions + simplifications

* removed `emit` from non-signal function calls.
* replaced `QStringLiteral("")` with a constexpr friendly
`QLatin1String()`

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

* Fix a CNewLevelDialog focus bug

Fixed an incorrect QTimer::singleShot invocation.

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

* match lambda to `messageChanged` signature

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

* vs compilation fix + applied review

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

* apply reviewer recommendation

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

Code/Editor/Controls/ReflectedPropertyControl/PropertyMiscCtrl.h

@@ -6,8 +6,6 @@
  *
  */
 
-#ifndef CRYINCLUDE_EDITOR_UTILS_PROPERTYMISCCTRL_H
-#define CRYINCLUDE_EDITOR_UTILS_PROPERTYMISCCTRL_H
 #pragma once
 
 #if !defined(Q_MOC_RUN)
@@ -53,6 +51,7 @@ private:
 
 class UserPopupWidgetHandler : public QObject, public AzToolsFramework::PropertyHandler < CReflectedVarUser, UserPropertyEditor>
 {
+    Q_OBJECT
 public:
     AZ_CLASS_ALLOCATOR(UserPopupWidgetHandler, AZ::SystemAllocator, 0);
     bool IsDefaultHandler() const override { return false; }
@@ -67,6 +66,7 @@ public:
 
 class FloatCurveHandler : public QObject, public AzToolsFramework::PropertyHandler < CReflectedVarSpline, CSplineCtrl>
 {
+    Q_OBJECT
 public:
     AZ_CLASS_ALLOCATOR(FloatCurveHandler, AZ::SystemAllocator, 0);
     bool IsDefaultHandler() const override { return false; }
@@ -80,5 +80,3 @@ public:
 
     void OnSplineChange(CSplineCtrl*);
 };
-
-#endif // CRYINCLUDE_EDITOR_UTILS_PROPERTYMISCCTRL_H