Allow users to specify Athena workgroup in Athena offline store config #3129

As mentioned in Slack channel #feast-aws, after testing the new Athena offline store, I found we are not able to specify Athena workgroup in AthenaOfflineStoreConfig or, more precisely, in the offline_store config of feature_store.yaml.

Possible solution: Add a workgroup attribute into AthenaOfflineStoreConfig

Here is the function that should accept a workgroup argument.