Change SystemApi as per API council feedback

API council have requested a manifest constant be added
to the SystemApi directly in preference to an indirect
SystemApi constant here:
android.provider.TimeZoneRulesDataContract.READER_PERMISSION.

This is the first of three changes to (1) add the new constant,
(2) switch over code using the constant, (3) remove the
constant.

Bug: 64568899
Test: None, build only
Change-Id: Ib9766591979886d1db3b1d7321536dabf5cf81a8
(cherry picked from commit 8bb4140516)

api/system-current.txt

@@ -263,6 +263,7 @@ package android {
     field public static final java.lang.String UPDATE_APP_OPS_STATS = "android.permission.UPDATE_APP_OPS_STATS";
     field public static final java.lang.String UPDATE_DEVICE_STATS = "android.permission.UPDATE_DEVICE_STATS";
     field public static final java.lang.String UPDATE_LOCK = "android.permission.UPDATE_LOCK";
+    field public static final java.lang.String UPDATE_TIME_ZONE_RULES = "android.permission.UPDATE_TIME_ZONE_RULES";
     field public static final java.lang.String USER_ACTIVITY = "android.permission.USER_ACTIVITY";
     field public static final java.lang.String USE_FINGERPRINT = "android.permission.USE_FINGERPRINT";
     field public static final java.lang.String USE_SIP = "android.permission.USE_SIP";

core/res/AndroidManifest.xml

@@ -2261,7 +2261,7 @@
          <p>An application requesting this permission is responsible for
          verifying the source and integrity of the update before passing
          it off to the installer components.
-         @hide -->
+         @SystemApi @hide -->
     <permission android:name="android.permission.UPDATE_TIME_ZONE_RULES"
         android:protectionLevel="signature|privileged" />