Refactor: scheduler: Change args to pe__unpack_dataset_nvpairs.

It should now take a pe_rule_eval_data_t instead of various separate
arguments. This will allow passing further data that needs to be tested
against in the future (such as rsc_defaults and op_defaults). It's also
convenient to make versions of pe_unpack_nvpairs and
pe_unpack_versioned_attributes that take the same arguments.

Then, adapt callers of pe__unpack_dataset_nvpairs to pass the new
argument.