Allow hex-encoded byte query vectors

[pquentin]

Added in elastic/elasticsearch#105393. Fixes the following test:

// Test file: /test/free/search.vectors/170_knn_search_hex_encoded_byte_vectors.yml
// Test name: Knn search with hex string for byte field

import { expectAssignable } from 'tsd'
import * as T from '../types'

expectAssignable<T.SearchRequest>({
  "body": {
    "knn": {
      "field": "my_vector_byte",
      "k": 10,
      "num_candidates": 100,
      "query_vector": "400ae2"
    },
    "size": 3
  },
  "index": "knn_hex_vector_index",
  "typed_keys": true
})

[github-actions]

Following you can find the validation changes against the target branch for the APIs.

API	Status	Request	Response
get	🟢	317/317 → 321/321	314/314 → 318/318
index	🟢	1440/1440 → 1445/1445	1442/1442 → 1447/1447
indices.create	🔴	1373/1397 → 1378/1402	1397/1397 → 1402/1402
indices.get_mapping	🔴	198/198 → 202/202	187/198 → 191/202
search	🔴	2584/2611 → 2589/2612	2611/2611 → 2612/2612

You can validate these APIs yourself by using the make validate target.