[upstream] Subscription configuration supports node affinity

Story: As an OLM user, I'd like to configure the Subscription API to allow multiple architecture values to be specified so I can install Operators to the matching architecture worker nodes in heterogeneous architecture clusters.

Note:

• This is to track the OLM changes to support node selection for "OpenShift for Heterogeneous Clusters".
• Ref: https://github.com/openshift/enhancements/pull/1014

Acceptance criteria:

• enable users to specify multiple nodes of different architectures in the config specification of a Subscription nodes using nodeAffinity