Adding option in global setting to control the display message during user switch

Bug: 145915635
Bug: 148457657
Fixes: 148504218

Test: adb shell settings put global android.car.ENABLE_USER_SWITCH_DEVELOPER_MESSAGE true
Merged-In: I64479733b0bb036a21a9291bac1448196a00a36c
Change-Id: I64479733b0bb036a21a9291bac1448196a00a36c
(cherry picked from commit 6449797e6fb00caee96b204e7f35878db5cb2415)
(cherry picked from commit 6a2788e67d799614c2151ea4be0dad052df12243)
(cherry picked from commit 7768187a2ea9f4c750a26ae7a093881af27a907d)
diff --git a/car-lib/src/android/car/settings/CarSettings.java b/car-lib/src/android/car/settings/CarSettings.java
index c307cab..35d7a34 100644
--- a/car-lib/src/android/car/settings/CarSettings.java
+++ b/car-lib/src/android/car/settings/CarSettings.java
@@ -76,6 +76,15 @@
          */
         public static final String DEFAULT_USER_RESTRICTIONS_SET =
                 "android.car.DEFAULT_USER_RESTRICTIONS_SET";
+
+        /**
+         * Developer settings String used to explicitly enable the user switch message when
+         * set to {@code "true"}.
+         *
+         * @hide
+         */
+        public static final String ENABLE_USER_SWITCH_DEVELOPER_MESSAGE =
+                "android.car.ENABLE_USER_SWITCH_DEVELOPER_MESSAGE";
     }
 
     /**