search: structural search uses literal search parser

Created by: rvantonder

Similar to #11480, structural search expects concatenated patterns to also be space-separated search patterns, so now uses the same parser as literal search before being handed off to comby.

Because the literal search parser interprets quotes literally (which is what we want), but the parser without and/or queries does not, I am activating the new parser unconditionally for structural search queries, and cover this behavior with integration tests.