cleanup: LiveQuery: state variables instead of booleans (#2789)
cleanup: LiveQuery: state variables instead of booleans (#2789)

* update status : live query update status is collected to make it as a update status variable.
* state : query state is defined by observing, stopping and stopped.
* Fixes part 2 CBL-795
couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios