When app wants to create activity through sidecar (for example,
startActivityToSide), we need a callback in case it failed to finish the
request.
Allow the caller to set a token for the WCT, which will be passed back
if there is any error, so that the caller can identify the error
callback.
Bug: 190433129
Test: N/A
Change-Id: Icffb7255e75465b90ed822559296f147a7e3418a
ccff5a6a8b