FluvioAdmin.list_partitions() return MetadataPartitionSpec should be populated with more info

[digikata]

MetadataPartitionSpec update

https://infinyon.github.io/fluvio-client-python/fluvio.html#MetadataTopicSpec output by calls like https://infinyon.github.io/fluvio-client-python/fluvio.html#FluvioAdmin.all_topics should also expand. It would be nice to could also simplfy this so input and output TopicSpec are the same (but this isn't a hard requirement)

Similar for https://infinyon.github.io/fluvio-client-python/fluvio.html#MetadataPartitionSpec returned by https://infinyon.github.io/fluvio-client-python/fluvio.html#FluvioAdmin.list_partitions

This could be broken off into smaller sub-issues or multiple PRs as needed.

Originally posted by @digikata in #527