Add lifecycle states to Session to help add clarity and ease of

maintenance to Sessions.

* mSessionState is the unique lifecycle State of the current Session.

* mSessionInfo contains metadata and other state identifying booleans
for the current Session.

Bug: 171350451
Bug: 162357598
Test: atest CtsAutoFillServiceTestCases
Change-Id: Id8cead9e5299b3f4e24c035706e04fa46555fc9b