Port open source rtsp_demo to replace librtsp

[KunYi]

I believe I’ve found the original open source codebase that librtsp is based on: rtsp_demo

However, it’s not exactly the same as the version currently in use. So, based on my understanding, I’ve ported a version and done some basic testing.

You can find the details here: my test commit

but the patches unstable now, random get error like the below message

rtsp://172.32.0.93/live/0: Server returned 4XX Client Error, but not one of 40{0,1,3,4}

Update, latest commit fix: "454 Session Not Found" issues