Add API support for multi-endpoint.

This CL includes changes required to support multi-endpoint (see the
design doc linked off the bug).

Main changes include:
- support for indicating if a call/connection is "external" to the device.
- support for indicating if an external call can be pulled from the
remote device to the local device.
- API used to initiate a pull of a call external to the current device to
the current device.
- Made the "connection event" API public (was previously @hide); this will
be used to support passing some error events involving pulling calls to
the incall ui.
- Added new InCallService metadata which will be used to determine if an
InCallService wants to be informed of external calls.
- New disconnect causes which will be used to expose the fact that a
multi-endpoint call was answered elsewhere and that a call ended because
it was pulled to another device.
- New call log call types to indicate if calls were answered elsewhere
or pulled to another device.

Bug: 27458894
Change-Id: I423f64ff965b5e50194635a51868c327782db2a1

telecomm/java/android/telecom/TelecomManager.java

@@ -316,6 +316,18 @@ public class TelecomManager {
     public static final String METADATA_IN_CALL_SERVICE_RINGING =
             "android.telecom.IN_CALL_SERVICE_RINGING";
 
+    /**
+     * A boolean meta-data value indicating whether an {@link InCallService} wants to be informed of
+     * calls which have the {@link Call.Details#PROPERTY_IS_EXTERNAL_CALL} property.  An external
+     * call is one which a {@link ConnectionService} knows about, but is not connected to directly.
+     * Dialer implementations (see {@link #getDefaultDialerPackage()}) which would like to be
+     * informed of external calls should set this meta-data to {@code true} in the manifest
+     * registration of their {@link InCallService}.  By default, the {@link InCallService} will NOT
+     * be informed of external calls.
+     */
+    public static final String METADATA_INCLUDE_EXTERNAL_CALLS =
+            "android.telecom.INCLUDE_EXTERNAL_CALLS";
+
     /**
      * The dual tone multi-frequency signaling character sent to indicate the dialing system should
      * pause for a predefined period.