Implement conversion of parquet to Delta tables

[gruuya]

Introduce an analogue to https://docs.databricks.com/en/sql/language-manual/delta-convert-to-delta.html

This should make use of delta-io/delta-rs#1686 behind the scenes. It should also work in-place (i.e. for parquet tables stored inside the Seafowl data dir) and optionally for parquet tables stored in other folders/buckets or even object stores.