Define `respond_to?` on `RecordRef` to match `method_missing` behavior

[cgunther]

RecordRefs often include a name, which allows access via method_missing by calling record_ref.name, however if no referenced record is assigned, you'll still get a RecordRef instance, it just wont have any fields, so record_ref.name raised a NoMethodError, but if you checked for the field first via record_ref.respond_to?(:name), it'd be falsey regardless of whether the field existed or not.

Defining respond_to? in good practice alongside method_missing. Ideally, respond_to_missing? would be used instead, as that enables access to the method like record_ref.method(:name), however I kept with respond_to? to match CustomFieldList.

CustomRecordRef also uses method_missing, however there's no specs and I'm not familiar with that record, so I left it alone.

[cgunther]

CI is failing because of an upstream change in Nori, which can be fixed by https://github.com/NetSweet/netsuite/pull/607