### 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
errorBuilder = new StringBuilder(
                            "element_type ["
                                + this
                                + "] vectors only support integers between ["
                                + Byte.MIN_VALUE
                                + ", "
                                + Byte.MAX_VALUE
                                + "] but found ["
                                + value
                                + "] at dim ["
                                + index
                                + "];"
                        );
                        break;
                    }
                }
                if (errorBuilder != null) {
                    throw new IllegalArgumentException(appendErrorElements(errorBuilder, vector).toString());
                }
            }
            @Override
            void checkVectorMagnitude(
                IndexVersion indexVersion,
                VectorSimilarity similarity,
                Function<StringBuilder, StringBuilder> appender,
                float squaredMagnitude
            ) {
                StringBuilder errorBuilder = null;
                if (similarity == VectorSimilarity.COSINE && Math.sqrt(squaredMagnitude) == 0.0f) {
                    errorBuilder = new StringBuilder(