Add more flexible background support to FullscreenDialog (#2675)

Hide the background when the main content extends underneath the bottom content.

ElementX/Sources/Screens/SecureBackup/SecureBackupLogoutConfirmationScreen/View/SecureBackupLogoutConfirmationScreen.swift

@@ -33,7 +33,7 @@ struct SecureBackupLogoutConfirmationScreen: View {
         }
         .toolbar { toolbar }
         .background()
-        .environment(\.backgroundStyle, AnyShapeStyle(Color.compound.bgCanvasDefault))
+        .backgroundStyle(.compound.bgCanvasDefault)
         .alert(item: $context.alertInfo)
     }