[FEA] Support decimal type in ORC writer

[firestarman]

cuDF has added decimal type support in ORC writer by the PR rapidsai/cudf#8198.

So we can enable the decimal support on plugin side now. Maybe just updating the type signature can have this done.

But this should need more work than just updating the type checks.

#3177 is for ORC reader

[jlowe]

This will need to be more involved than just updating type checks. Unlike reading where we can rely on Spark conveying to us the expected decimal precision in the read schema, we need to tell cudf the decimal precision to write. The scale can be automatically detected based on the cudf type, but cudf does not track precision. For example, we may want to write a type that's Decimal(10,2) but there's currently no way to specify to the cudf ORC writer that the decimal precision of the column in the ORC file needs to be 10.

[GaryShen2008]

@Salonijain27 This issue depends on cuDF to support specifying precision of Decimal, which is not implemented yet. Can we move it to 21.12 plan? Of course, need to confirm with cuDF team.

[sameerz]

Marking as P1 for 21.12.

[GaryShen2008]

This issue is related. rapidsai/cudf#9319