Update ContentCaptureContext to have a token information

In order to support auto translation, we need to give information to
content capture service to let the app can use this information to
find the Activity which needed to be translated.

It's not safe to provide an activity token to the client app directly
even if it is a privilege app. They can use this activity token to
access many activity/windows related functions. We create a new token
for use for content capture and translation. This token will be used
get the target Activity for translation new APIs.

This change focuses on the Content capture API change, the API change
about translation will be done in the next change,

Bug: 177789967
Test: manual. Make sure cc service can get the information.
Test: atest android.view.contentcapture.ContentCaptureContextTest
Test: atest CtsContentCaptureServiceTestCases

Change-Id: Ife8096a8bd1e71ce4e686d95043e347222ad7ee6