### Description

Dynamic mappings can greatly help the getting started experience but they currently don't apply to all types, one example is `dense_vector`.

It's been suggested to automatically map float arrays as dense vectors when there are more than 100 values, or a heuristic along these lines.
server/src/internalClusterTest/java/org/elasticsearch/index/mapper/DynamicMappingIT.java
"properties": {
                  "obj": {
                    "properties": {
                      "runtime": {
                        "properties": {
                          "dynamic": {
                            "type": "object",
                            "dynamic": true
                          }
                        }
                      }
                    }
                  }
                }
              }
            }""", XContentType.JSON));
        
        
        
        assertEquals(
            RestStatus.CREATED,
            client().prepareIndex("test")
                .setSource("obj.runtime.dynamic.number", 1)
                .setId("id")
                .setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE)
                .get()
                .status()
        );
        {
            SearchResponse searchResponse = client().prepareSearch("test")