Better whylabs support for logged images

[richard-rogers]

This depends on #860

It adds a resolver to the ImageMetric analogous to the DatasetSchema's to create the standard metrics (counts, types, cardinality, etc.) that the visualizer & whylabs seem to require. The logical submetric name is prefixed with a metric type code so that the related metrics can be aggregated into some ColumnProfileView when the ImageMetric is "uncompounded" to send it to whylabs.