The helper in question is used in several different ways -- by handlers directly (most of the callers), as a part of wrap_ks_cf() helper and by one of its overloads that unpack the "cf" query parameter from request. This PR generalizes most of the described callers thus reducing the number differently-looking of ways API handlers parse "keyspace" and "cf" request parameters.
Continuation of #22742Closesscylladb/scylladb#23368
* github.com:scylladb/scylladb:
api: Squash two parse_table_infos into one
api: Generalize keyspaces:tables parsing a little bit more
api: Provide general pair<keyspace, vector<table>> parsing
api: Remove ks_cf_func and related code