add support for delete from tbl

[djouallah]

when using delta, delete from tbl where field = 'something" does not work, will be nice to support it :)

[linhr]

Thanks for this feature request!

We're working on revamping the internals of our Delta Lake integration to make the physical plan nodes for Delta write operations more composable. This will allow us to support conditional updates/deletes in the near future.