### 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/main/java/org/elasticsearch/index/mapper/DocumentParserContext.java
* because for dynamic mappings, a new field can be either mapped
     * as runtime or indexed, but never both.
     */
    final void addDynamicRuntimeField(RuntimeField runtimeField) {
        if (newFieldsSeen.add(runtimeField.name())) {
            mappingLookup.checkFieldLimit(indexSettings().getMappingTotalFieldsLimit(), newFieldsSeen.size());
        }
        dynamicRuntimeFields.add(runtimeField);
    }
    /**
     * Get dynamic runtime fields created while parsing. Holds a flat set of {@link RuntimeField}s.
     * Runtime fields get dynamically mapped when {@link org.elasticsearch.index.mapper.ObjectMapper.Dynamic#RUNTIME} is used,
     * or when dynamic templates specify a <code>runtime</code> section.
     */
    public final List<RuntimeField> getDynamicRuntimeFields() {
        return Collections.unmodifiableList(dynamicRuntimeFields);
    }
    /**
     * Returns an Iterable over all non-root documents. If there are no non-root documents
     * the iterable will return an empty iterator.
     */
    public abstract Iterable<LuceneDocument> nonRootDocuments();
    /**
     * @return a RootObjectMapper.Builder to be used to construct a dynamic mapping update
     */
    public final RootObjectMapper.Builder updateRoot() {
        return mappingLookup.getMapping().getRoot().newBuilder(mappingParserContext.getIndexSettings().getIndexVersionCreated());
    }
    public boolean isWithinCopyTo() {
        return false;