[Feature] Add efficient k-NN filtering support to Neural query

[SeyedAlirezaFatemi]

Is your feature request related to a problem?

Currently, there is no way to use efficient k-NN filtering with a Neural query (documentation)

What solution would you like?

Adding a filter field to the neural query which is pretty similar to the syntax of efficient k-NN filtering:

"neural": {
  "<vector_field>": {
    "query_text": "<query_text>",
    "query_image": "<image_binary>",
    "model_id": "<model_id>",
    "k": 100,

    "filter": {
      ...
    }

  }
}