higress support ext_authz wasmplugin

[alexzzh]

Why do you need it?

• 项目上需要用到ext_auth插件，但又不想通过后台apply ext_authz的envoyfilter来解决
• 想了解higress 针对该wasm插件的规划(是否有计划支持以及大致时间)，可以描述一下，以便进以及有相同需求的用户知悉

How could it be?

A clear and concise description of what you want to happen. You can explain more about input of the feature, and output of it.

Other related information

• 相关PR: feautre: support ext-authz by annotation  #263 通过注解来实现ext_authz

[johnlanni]

参考envoy原生filter：https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_filters/ext_authz_filter

实现原生filter中对接HTTP服务的部分能力即可

[hanxiantao]

申请这个任务，麻烦帮忙分配一下 @johnlanni