API Review cleanups.

- New @SystemApis on Conference and PhoneAccount were missing the required
permissions annotations.
- Rename PROPERTY_ASSISTED_DIALING_USED to PROPERTY_ASSISTED_DIALING
- Standardize get/setConnectionStartElapsedRealtimeMillis method naming
across Connection and Conference classes.
- Clarify Conference#sendConferenceEvent API documentation to match the
docs present for similar method in Connection; include some examples of
valid event/extras combinations.
- Update TelecomManager#getDefaultdialerPackage to use UserHandle instead
of userId.
- Move Conference#getConnectionStartElapsedRealtimeMillis to public API
since the setter is already part of the public API.

Test: Run Telecom and Telephony CTS tests.
Test: Run Telephony unit tests.
Test: Perform manual single-party-conference regression test to confirm
that conference behavior does not regress.

Bug: 147301297
Bug: 148286830
Bug: 148284863
Bug: 148284843
Bug: 148287068
Bug: 148285484
Bug: 148285560
Change-Id: I1f446d81859fa109d74af3661a42a0bd224de5aa
Merged-In: I1f446d81859fa109d74af3661a42a0bd224de5aa
diff --git a/telecomm/java/android/telecom/PhoneAccount.java b/telecomm/java/android/telecom/PhoneAccount.java
index abb210f..6ae4a08 100644
--- a/telecomm/java/android/telecom/PhoneAccount.java
+++ b/telecomm/java/android/telecom/PhoneAccount.java
@@ -16,7 +16,10 @@
 
 package android.telecom;
 
+import static android.Manifest.permission.MODIFY_PHONE_STATE;
+
 import android.annotation.NonNull;
+import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.content.Intent;
@@ -605,7 +608,8 @@
          * time. By default, there is no group Id for a {@link PhoneAccount} (an empty String). Only
          * grouped {@link PhoneAccount}s with the same {@link ConnectionService} can be replaced.
          * <p>
-         * Note: This is an API specific to the Telephony stack.
+         * Note: This is an API specific to the Telephony stack; the group Id will be ignored for
+         * callers not holding the correct permission.
          *
          * @param groupId The group Id of the {@link PhoneAccount} that will replace any other
          * registered {@link PhoneAccount} in Telecom with the same Group Id.
@@ -614,6 +618,7 @@
          */
         @SystemApi
         @TestApi
+        @RequiresPermission(MODIFY_PHONE_STATE)
         public @NonNull Builder setGroupId(@NonNull String groupId) {
             if (groupId != null) {
                 mGroupId = groupId;