[RFC] Add fundamental traffic governance building blocks in Sentinel 2.0 | 流量治理功能骨架与抽象

[sczyh30]

Issue Description

Type: feature request

Describe what happened (or what feature you want)

Sentinel 2.0 will evolve to a universal, cloud-native traffic governance component. Thus we'll need to add fundamental traffic governance building blocks in Sentinel 2.0, which at-least cover:

• A local "brain" for hinting load balancing [RFC] Local "brain" abstraction for hinting load balancing and routing #2944
• Traffic routing Umbrella issue for traffic routing implementation of Sentinel 2.0 #2846
• Traffic tagging as well as carrying tags between services
• Outlier eviction

This is the umbrella issue of traffic governance building blocks in Sentinel 2.0.

Related issues: #2845 (regarding API model)

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Sentinel 2.0 将演进为通用、云原生的流量治理组件，并天然支持 OpenSergo 流量治理标准。Sentinel 1.x 的 API 与场景均基于流量策略来进行设计，而未干预流量到来之前的过程，以及中间的执行过程。在 Sentinel 2.0 中，我们需要扩充这一部分的抽象，来支持更多的流量治理能力，其中包括但不限于：

• 本地的决策组件，基于给定的流量与条件来为 load balancing 与 routing 提供 hint
• 流量路由流程的抽象
• 流量染色与标透传的流程抽象
• 异常实例摘除、熔断

[XW512]

I'm looking forward to the official release of this version