What this PR does / why we need it:

This PR making the feast vector store api with open ai search api compatible so.

the current changes are creating an new rest api end point which is compatible with open ai search api and also it include an extra field in the metadata named features_to_retrieve(allows to retrieve specific feature) and content_field (which field include the main content or Chunk document)

what things are missing :

 1. It only supports the normal query string need to have some embedding mode which embed the query string.
 2. If need it could also support the feature service
 3. Support the filters params (Require changes in the vector store retrieve query.) 

Which issue(s) this PR fixes:

#5615

Misc