database: move and rename: classify_query -> classify_request
database: move and rename: classify_query -> classify_request

Moves the classify_query higher and renames it to classify_request. The
function will be reused in further commits to protect non-user queries
from accidentally being rate limited.

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla