[TASK] Rename cache serializer to a common name

[jlowe]

After #2905 all that remains is the Spark 3.1.1 cache serializer but it is common to all Spark versions that support a pluggable cache serializer. This class should be renamed to a common package and moved out of the Spark 3.1.1 shim project.

[sperlingxx]

I am wondering how to adapt Spark 3.0.x if we move the serializer to common package. The CachedBatchSerializer was introduced at 3.1.

[jlowe]

The module would be common to all Spark versions >= 3.1.1 rather than in a specific shim directory as it is now. That module would not compile against Spark 3.0.x.

[Salonijain27]

duplicate of #3314