Editor code: tidy up BOOLs,NULLs and overrides pt5. (#2876)

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 5 of a split #2847

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

Co-authored-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/CustomResolutionDlg.cpp

@@ -25,7 +25,7 @@ AZ_POP_DISABLE_DLL_EXPORT_MEMBER_WARNING
 #define MIN_RES 64
 #define MAX_RES 8192
 
-CCustomResolutionDlg::CCustomResolutionDlg(int w, int h, QWidget* pParent /*=NULL*/)
+CCustomResolutionDlg::CCustomResolutionDlg(int w, int h, QWidget* pParent /*=nullptr*/)
     : QDialog(pParent)
     , m_wDefault(w)
     , m_hDefault(h)
@@ -50,12 +50,12 @@ void CCustomResolutionDlg::OnInitDialog()
     m_ui->m_height->setValue(m_hDefault);
 
     QString maxDimensionString;
-    QTextStream(&maxDimensionString) 
-        << "Maximum Dimension: " << MAX_RES << Qt::endl 
+    QTextStream(&maxDimensionString)
+        << "Maximum Dimension: " << MAX_RES << Qt::endl
         << Qt::endl
         << "Note: Dimensions over 8K may be" << Qt::endl
         << "unstable depending on hardware.";
-    
+
     m_ui->m_maxDimension->setText(maxDimensionString);
 }