feat: sse-timing plugin for tracing events

[jizhuozhi]

Ⅰ. Describe what this PR did

Add sse-timing plugin for tracing timestamp that each event received in higress. An alternative implementation of the server-timing protocol (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing). It's useful to profile AI backend latency which uses event-stream MIME type.

And implemention an EventStream for common SSE(text/event-stream) parsing.

Ⅱ. Does this pull request fix one issue?

None

Ⅲ. Why don't you add test cases (unit test/integration test)?

I'm sorry I don't know how to add WASM testcase, we could discuss in this PR.

Ⅳ. Describe how to verify it

There is a docker-compose.yml in plugin directory, with a go server backend which provides sse response, up it and then just use broswer to open http://localhost:10000, you could see events in dev-tools.

Ⅴ. Special notes for reviews