### 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/vectors/DenseVectorFieldMapper.java
int dims,
        boolean indexed,
        VectorSimilarity similarity,
        IndexOptions indexOptions,
        IndexVersion indexCreatedVersion,
        MultiFields multiFields,
        CopyTo copyTo
    ) {
        super(simpleName, mappedFieldType, multiFields, copyTo);
        this.elementType = elementType;
        this.dims = dims;
        this.indexed = indexed;
        this.similarity = similarity;
        this.indexOptions = indexOptions;
        this.indexCreatedVersion = indexCreatedVersion;
    }
    @Override
    public DenseVectorFieldType fieldType() {
        return (DenseVectorFieldType) super.fieldType();
    }
    @Override
    public boolean parsesArrayValue() {
        return true;
    }
    @Override
    public void parse(DocumentParserContext context) throws IOException {
        if (context.doc().getByKey(fieldType().name()) != null) {
            throw new IllegalArgumentException(
                "Field ["
                    + name()