Reloads search analyzers are unsupported for synonym_graph

[kasa-taku]

Elasticsearch v7.3.0

The Indices-reload-analyzers document says "both synonym and synonym_graph", but only "synonym" filter is supported.
https://www.elastic.co/guide/en/elasticsearch/reference/7.3/indices-reload-analyzers.html#indices-reload-analyzers

1.Create Index

PUT test/
{
  "settings": {
    "index": {
      "number_of_shards": "1",
      "number_of_replicas": 0,
      "analysis": {
        "filter": {
          "synonym": {
            "type": "synonym",
            "synonyms_path": "synonyms.txt",
            "updateable" : true
          },
          "synonym_graph": {
            "type": "synonym_graph",
            "synonyms_path": "synonyms.txt",
            "updateable" : true
          }
        },
        "analyzer": {
          "synonym_analyzer": {
            "type": "custom",
            "tokenizer": "whitespace",
            "filter": [
              "synonym"
            ]
          },
          "synonym_graph_analyzer": {
            "type": "custom",
            "tokenizer": "whitespace",
            "filter": [
              "synonym_graph"
            ]
          }
        }
      }
    }
  }
}

2.Reloads search analyzers API

POST test/_reload_search_analyzers

3.Returns with
reloaded_analyzers is only "synonym_analyzer".

{
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "reload_details" : [
    {
      "index" : "test",
      "reloaded_analyzers" : [
        "synonym_analyzer"
      ],
      "reloaded_node_ids" : [
        "ATMfHkMvTKmhp7WSNcVlPA"
      ]
    }
  ]
}

[elasticmachine]

Pinging @elastic/es-search

[cbuescher]

Thanks @kasa-taku for reporting this and the great reproduction. I opened #45135 to fix this.