Introduce default font size. This fixes sizing and spacing for text rendered via a painter with not font specified. (#4069)

Also removed some qss for windows that have been removed.

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

Code/Editor/Style/Editor.qss

@@ -191,94 +191,4 @@ ConsoleTextEdit:focus,
     border-width: 0px;
     border-color: #e9e9e9;
     border-style: solid;
-}
-
-/* Welcome Screen styling */
-
-WelcomeScreenDialog QLabel
-{
-    font-size: 12px;
-    color: #FFFFFF;
-    line-height: 20px;
-    background-color: transparent;
-    margin: 0;
-}
-
-WelcomeScreenDialog QLabel#currentProjectLabel
-{
-    margin-top: 10px;
-}
-
-WelcomeScreenDialog QPushButton
-{
-    font-size: 14px;
-    line-height: 16px;
-}
-
-WelcomeScreenDialog QWidget#articleViewContainerRoot
-{
-    background: #444444;
-}
-
-WelcomeScreenDialog QWidget#levelViewFTUEContainer
-{
-    background: #282828;
-}
-
-QTableWidget#recentLevelTable::item {
-	background-color: rgb(64,64,64);
-	margin-bottom: 4px;
-	margin-top: 4px;
-}
-
-/* Particle Editor */
-
-#NumParticlesLabel
-{
-    margin-top: 6px;
-}
-
-#LibrarySearchIcon
-{
-    max-width: 16px;
-    max-height: 16px;
-    qproperty-iconSize: 16px 16px;
-}
-
-
-#ClosePrefabDialog, #SavePrefabDialog
-{
-    min-width : 640px;
-}
-
-#SaveDependentPrefabsCard
-{
-    margin: 0px 15px 10px 15px;
-}
-
-#PrefabSavedMessageFrame{
-    border: 1px solid green;
-    margin: 10px 15px 10px 15px;
-    border-radius: 2px;
-    padding: 5px 2px 5px 2px;
-}
-
-#ClosePrefabDialog #PrefabSaveWarningFrame
-{
-    border: 1px solid orange;
-    margin: 10px 15px 10px 15px;
-    border-radius: 2px;
-    padding: 5px 2px 5px 2px;
-    color : white;
-}
-
-#SavePrefabDialog #FooterSeparatorLine
-{
-    color: gray;
-}
-
-#SavePrefabDialog #PrefabSavePreferenceHint
-{
-    font: italic;
-    color: #999999;
 }

Code/Framework/AzQtComponents/AzQtComponents/Components/StyleManager.cpp

@@ -169,6 +169,10 @@ namespace AzQtComponents
         initializeSearchPaths(application, engineRootPath);
         initializeFonts();
 
+        QFont defaultFont("Open Sans");
+        defaultFont.setPixelSize(12);
+        QApplication::setFont(defaultFont);
+
         m_titleBarOverdrawHandler = TitleBarOverdrawHandler::createHandler(application, this);
 
         // The window decoration wrappers require the titlebar overdraw handler