### 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
mappings.startArray("dynamic_templates");
            {
                mappings.startObject();
                mappings.startObject("location");
                {
                    if (randomBoolean()) {
                        mappings.field("match", "location");
                    }
                    if (randomBoolean()) {
                        mappings.field("match_mapping_type", "string");
                    }
                    mappings.startObject("mapping");
                    {
                        mappings.field("type", "geo_point");
                    }
                    mappings.endObject();
                }
                mappings.endObject();
                mappings.endObject();
            }
            mappings.endArray();
        }
        mappings.endObject();
        assertAcked(indicesAdmin().prepareCreate("test").setMapping(mappings));
        List<IndexRequest> requests = new ArrayList<>();
        requests.add(
            new IndexRequest("test").id("1").source("location", "41.12,-71.34").setDynamicTemplates(Map.of("location", "location"))
        );
        requests.add(
            new IndexRequest("test").id("2")