refactor: use pattern type only in query alert suggestions

Created by: rvantonder

The patternType is only needed when an alert has suggestions. It is now part of

proposedQueries []*searchQueryDescription

instead of the alert type. This change removes all the places that patternType is needlessly specified when constructing alerts, and adds it explicitly when constructing suggestions.

This change also makes it possible to construct multiple suggestions per alert with different pattern types. E.g., "You did this in literal search? Suggest this query in regex search or structural search".