Keystore 2.0: Add namespace locksettings.

This namespace is required by LocksettingsService to protect the
synthetic password key from removal when the user removes the
credentials or wipes AID_SYSTEM app data.

Bug: 184664830
Test: N/A
Change-Id: Ie752a75d2cb2ebf1f4e5814bc2cbc807cc754c21

keystore/java/android/security/keystore/KeyProperties.java

@@ -904,6 +904,7 @@ public abstract class KeyProperties {
     @IntDef(prefix = { "NAMESPACE_" }, value = {
             NAMESPACE_APPLICATION,
             NAMESPACE_WIFI,
+            NAMESPACE_LOCKSETTINGS,
     })
     public @interface Namespace {}
 
@@ -924,6 +925,13 @@ public abstract class KeyProperties {
     @SystemApi
     public static final int NAMESPACE_WIFI = 102;
 
+    /**
+     * The namespace identifier for the LOCKSETTINGS Keystore namespace.
+     * This must be kept in sync with system/sepolicy/private/keystore2_key_contexts
+     * @hide
+     */
+    public static final int NAMESPACE_LOCKSETTINGS = 103;
+
     /**
      * For legacy support, translate namespaces into known UIDs.
      * @hide