patternType:standard mislabels regexp patterns inside parenthesis as literal patterns

Created by: coury-clark

Search queries with a pattern field that should be interpreted as regexp (inside /.../) will instead parse as literal if the pattern is wrapped in parenthesis. Examples:

insight[s] is parsed as literal and returns no matches /insight[s]/ is parsed as regexp and returns matches (/insight[s]/) is parsed as a literal and returns no matches.

This can be verified by checking the annotations in the query parser.

(/asdf/) lang:go query.SearchTypeStandard

msg=annotations: labels="[HeuristicParensAsPatterns Literal]"

/cc @benvenker @lguychard