HUE-7738 [editor] Add function listing in autocomplete API This is a first pass before v1. See the documentation for usage. Note: - only Hive can provide detailed function info - by default Hive only provides function names Still need to add: Both: - add other fields when possible, e.g. return type, signature, binary type, is persistent - show aggregate functions; - show analytic functions; Hive: - DESCRIBE FUNCTION EXTENDED trunc Impala - include _impala_builtins per default - include the active database Other SQL - TODO: either errors or try to return columns - MySql e.g. show function status (or better check with SqlAlchemy)