flumeview-sql: test query for threads

[ahdinosaur]

query is something like: "most recent root messages between seq ${start} and seq ${end}, not started by someone in the block list [${blocked}], not a private message, and you started the thread or have posted a branch message in the thread or have been mentioned in the thread"

we want to confirm we support this query, or if we need to add new tables / columns to support this query.