Add labels mechanism and actor-affinity-feature proposal

[larrylian]

1. Labels mechanism.

Introduce the Labels mechanism. Give Labels to Actors/Nodes. Affinity features such as ActorAffinity/NodeAffinity can be realized through Labels.

Read reps/2022-11-23-labels-mechanish-and-affinity-schedule-feature.md first.

2. Actor-Affinity Feature

Provides a set of lightweight actor affinity and anti-affinity scheduling interfaces. Replacing the heavy PG interface to implement collocate or spread actors.

• Affinity
  • Co-locate the actors in the same node.
  • Co-locate the actors in the same batch of nodes, like nodes in the same zones
• Anti-affinity
  • Spread the actors of a service across nodes and/or availability zones, e.g. to reduce correlated failures.
  • Give a actor "exclusive" access to a node to guarantee resource isolation
  • Spread the actors of different services that will affect each other on different nodes.