Add and/or query parser scaffolding

Created by: rvantonder

• Adds a site setting to activate a code path that uses the and/or query parser for input. The setting is not meant to be activated now, but later. Right now it's a way for me to develop against the code path.
• Adds an interim type QueryInfo which is an interface that either refers to our current query logic (type OrdinaryQuery) or type AndOrQuery (which is the new part I'll be filling in).

I introduced typeQueryInfo because it's going to be a real challenge for me to migrate the current query logic otherwise. We also want to preserve a fall back while transitioning. I've extracted the essential interface of Query so that most dependencies on query-related things do not know what the underlying type is. Over time, I will be trimming/renaming the QueryInfo interface. When we are ready to switch over to only AndOrQuery, QueryInfo will disappear, and AndOrQuery will simply become Query.

Created by: codecov[bot]

Codecov Report

Merging #9208 into master will decrease coverage by 0.01%. The diff coverage is 33.96%.

@@            Coverage Diff             @@
##           master    #9208      +/-   ##
==========================================
- Coverage    41.5%   41.48%   -0.02%     
==========================================
  Files        1315     1316       +1     
  Lines       71525    71585      +60     
  Branches     6601     6601              
==========================================
+ Hits        29686    29697      +11     
- Misses      39107    39154      +47     
- Partials     2732     2734       +2

Impacted Files	Coverage Δ
internal/search/types.go	0% <ø> (ø)
internal/conf/computed.go	18.64% <0%> (-0.55%)
cmd/frontend/graphqlbackend/search_commits.go	40.48% <0%> (ø)
cmd/frontend/graphqlbackend/search_symbols.go	10.62% <0%> (ø)
cmd/frontend/graphqlbackend/search_alert.go	17.98% <0%> (ø)
cmd/frontend/graphqlbackend/search_repositories.go	80.23% <100%> (ø)
cmd/frontend/graphqlbackend/textsearch.go	49.31% <100%> (+0.11%)
cmd/frontend/graphqlbackend/codemod.go	13.4% <100%> (ø)
cmd/frontend/graphqlbackend/search_suggestions.go	73.18% <100%> (ø)
internal/search/query/parser.go	89.75% <16.66%> (ø)
... and 5 more