### 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/test/java/org/elasticsearch/index/mapper/DynamicMappingTests.java
b.startObject("foo").startObject("bar").field("baz", 1).endObject().endObject();
            }
            b.endObject();
        }));
        assertEquals(XContentHelper.stripWhitespace("""
            {
              "_doc": {
                "dynamic": "runtime",
                "runtime": {
                  "object.foo.bar.baz": {
                    "type": "long"
                  }
                },
                "properties": {
                  "dynamic_object": {
                    "dynamic": "true",
                    "properties": {
                      "foo": {
                        "properties": {
                          "bar": {
                            "properties": {
                              "baz": {
                                "type": "long"
                              }
                            }
                          }
                        }
                      }
                    }
                  }