Refactor catalog/stores so the stores are unaware of the catalog

[abellina]

Currently the RapidsBufferStore and subclasses define the spill cadance (who is my spill store) and they also rely on the catalog for unspill. This task is to completely remove the link store->catalog, enforcing a strict catalog->store flow.

We want to then make as much as possible private under the com.nvidia.spark.rapids.spill package. RapidsBufferCatalog has public methods that allow entry into this namespace.