Update Splashscreen and About Us dialogs for General Availability (#4901)

* Add new image for splashscreen. Layout changes incoming.

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

* Adapt layouts to new splashscreen style with transparent background.

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

* Ensure cropping logic works correctly when screen scaling is used.

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

* Remove old image. Replace new image with new version with more readable credits.

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

Code/Editor/AboutDialog.ui

@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>600</width>
-    <height>360</height>
+    <height>300</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -19,13 +19,13 @@
   <property name="minimumSize">
    <size>
     <width>600</width>
-    <height>360</height>
+    <height>300</height>
    </size>
   </property>
   <property name="maximumSize">
    <size>
-    <width>600</width>
-    <height>360</height>
+    <width>608</width>
+    <height>300</height>
    </size>
   </property>
   <property name="windowTitle">
@@ -69,7 +69,7 @@
           <number>11</number>
          </property>
          <property name="topMargin">
-          <number>12</number>
+          <number>10</number>
          </property>
          <property name="bottomMargin">
           <number>12</number>
@@ -125,7 +125,7 @@
             </size>
            </property>
            <property name="text">
-            <string>Developer Preview</string>
+            <string>General Availability</string>
            </property>
            <property name="textFormat">
             <enum>Qt::AutoText</enum>