Use a better way of expressing 'Optional' parameters in the Binding Cluster

[vivien-apple]

I would prefer that we either explicitly use Optional to represent not-passed things here, or have a struct that can represent "either group id or (node, endpoint) pair" or something...

Probably ok to land as-is for now to unblock things, but please file a followup on fixing this?

Originally posted by @bzbarsky-apple in #4156 (comment)

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This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.