[DISCUSSION] Make OpenSergo module embedded in Sentinel Go

[sczyh30]

Issue Description

Type: feature request

Describe what feature you want

Make OpenSergo module (i.e. data-source with OpenSergo client) embedded in Sentinel Go, and support relevant config in sentinel.yml so that users may enable OpenSergo support without refactoring any code.

This arrangement indicates that Sentinel Go will internally support OpenSergo spec by default.

将 OpenSergo 适配模块作为 Sentinel Go 本身的一部分，并且支持通过 sentinel.yml 配置的方式来灵活启用 OpenSergo spec 支持，从而可以简化用户通过标准方式来配置流量治理规则。

Additional context

NOTE: this may introduce indirect dependencies including grpc-go and others.