* HLRC: ML Add preview datafeed api
* Changing deprecation handling for parser
* Removing some duplication in docs, will address other APIs in another PR
* HLRC: ML Cleanup docs
* updating get datafeed stats docs
This also changes both `DatafeedConfig` and `DatafeedUpdate`
to store the query and aggs as a bytes reference. This allows
the client to remove its dependency to the named objects
registry of the search module.
Relates #29827