[BUG] Round robin partitioning sort check falls back to CPU for cases that can be supported

[jlowe]

In GpuShuffleExchangeExecBase, tagPlanForGpu checks if the partitioning is round-robin and sort before repartition is enabled. If so, it then checks whether the types are orderable by the GPU. There's a GpuOverrides.pluginSupportedOrderableSig value that should be everything we support sorting on, but it's missing decimal128 and structs. Most places are manually tacking these on, but this is one that missed structs.

Ideally we should cleanup pluginSupportedOrderableSig to be everything we support sorting on, and add tests for repartitioning-with-sorting for struct types that are GPU orderable.

[ttnghia]

Depends on:

• Fully support lexicographic comparison for nested types in table self-comparator rapidsai/cudf#12879

[jlowe]

This does not depend on the cudf issue. This is a bug in the type check logic in the plugin where what is already supported by cudf, even before the mentioned cudf issue, is not always used.