Search endpoint fixes

[l-trotta]

Slowly increasing validation score for search.

• reason in ErrorCause can be "null", not just missing (source: I trust the recordings for this one)
• in GeoGridQuery geogrid is actually called geotile (source: server code)
• Missing RescorerRetriever in RetrieverContainer (source: server code)
• ruleset_ids in RuleRetriever can also accept string (not going to check it's always like this with string arrays)
• RuleQuery has both ruleset_ids and ruleset_id (which is the same just in a string format) (source: server code)
• Missing IntervalRange and IntervalRegexp in IntervalsContainer (source: server code)
• WeightedTokensQuery's tokens is actually a list of WeightedToken objects, but since the field is a sting let's make it a list of Single Key Dictionaries (source: server code)
• HighlightField is also a Single Key Dictionary (one or many) (source: server code)

The last 2 are breaking changes for static clients so I'm wondering if we should even introduce them just for the sake of validation, since it's not really broken, but it currently does not comply 100% with what the server can accept.

[github-actions]

Following you can find the validation results for the API you have changed.

API	Status	Request	Response
search	🔴	2349/2401	2385/2385

You can validate this API yourself by using the make validate target.

[l-trotta]

2349/2401 2385/2385

before it was 2316/2401 2384/2385

[flobernd]

LGTM from my side.

I would as well be fine with the breaking changes.

Btw: I think there is another retriever missing (the LinearRetriever).