Apply @hide / @SystemApi to android.telecom.*

Move the android.telecom.* namespace back to @hide, and also mark it
with @SystemApi so that system-privileged apps can use them.

Bug: 18302450
Change-Id: I33ae1b9b0dfdb1c5eff51ca3c829196bcfc9411c
diff --git a/telecomm/java/android/telecom/PhoneAccount.java b/telecomm/java/android/telecom/PhoneAccount.java
index 3fc1d3d..f9ee5d2 100644
--- a/telecomm/java/android/telecom/PhoneAccount.java
+++ b/telecomm/java/android/telecom/PhoneAccount.java
@@ -16,6 +16,7 @@
 
 package android.telecom;
 
+import android.annotation.SystemApi;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.pm.PackageManager;
@@ -45,7 +46,9 @@
  * alternative options when placing a phone call. When building a {@link PhoneAccount}, the app
  * should supply a valid {@link PhoneAccountHandle} that references the {@link ConnectionService}
  * implementation Telecom will use to interact with the app.
+ * @hide
  */
+@SystemApi
 public class PhoneAccount implements Parcelable {
 
     /**