UC Volume support

[gergo-databricks]

Support Unity Catalog Volumes by implementing VolumePath and add a function to automatically create the right path from a string based on the different referencing options (https://docs.databricks.com/en/files/index.html#do-i-need-to-provide-a-uri-scheme-to-access-data).

[gergo-databricks]

@nfx Can you give me permission to create a feature branch and open a PR? I already have the implementation.