Fix issue with spark "show tables" command when lakehouse has schemas

[JohnMiner3]

The show tables spark function should be lakehouse aware.  If it is without a schema, then search the root of the catalog.  If it has the schemas option enabled, then default to the "dbo" schema.  Otherwise, allow a "schema name" to be passed as an option.

A work around for now is the mssparkutils.fs.ls("Tables/Schema").  Then filter by any folder names only, these are the table directories.

Here is a screen shot for a schema less Fabric Lakehouse that works as expected.

Please fix this bug!