Implement receiver affinity

There should be a way to establish affinity in the invocation context, either to a node, a cluster, or a node within a cluster, to handle various situations like:

• Local transaction controlling a single remote node
• Proxy session is "stuck" to a node

The affinity should come in multiple flavors:

• "Strong" affinity - the request cannot complete if the affinity is broken (e.g. user transaction)
• "Weak" affinity - the request can ignore the affinity setting if the target is unavailable (e.g. cluster association)