add: whepfrom rtsp client mode

[Marsyew]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0.87336% with 227 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
livetwo/src/rtspclient.rs	0.00%	224 Missing ⚠️
livetwo/src/whep.rs	50.00%	2 Missing ⚠️
livetwo/src/whip.rs	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
livetwo/src/whip.rs	61.22% <0.00%> (+1.74%)	⬆️
livetwo/src/whep.rs	70.11% <50.00%> (-0.03%)	⬇️
livetwo/src/rtspclient.rs	7.19% <0.00%> (-2.97%)	⬇️

[a-wing]

I try use:

           WHEP              RTSP
Live777 --------> WhepFrom -------> mediamtx

There has some error

cargo run --bin=whepfrom -- -w http://localhost:7777/whip/web-0 -o rtsp://localhost:8554/mystream -vvv
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.36s
     Running `target/debug/whepfrom -w 'http://localhost:7777/whip/web-0' -o 'rtsp://localhost:8554/mystream' -vvv`
2025-01-06T07:24:08.082183Z  INFO ThreadId(01) livetwo::whep: livetwo/src/whep.rs:61: === Received Output: rtsp://localhost:8554/mystream ===
2025-01-06T07:24:18.159802Z DEBUG ThreadId(01) livetwo::whep: livetwo/src/whep.rs:347: Get http header link ice servers: [RTCIceServer { urls: ["stun:stun.l.google.com:19302"], username: "", credential: "", credential_type: Unspecified }]
2025-01-06T07:24:18.419136Z  WARN ThreadId(13) livetwo::whep: livetwo/src/whep.rs:419: Connection state changed: connected
2025-01-06T07:24:19.169289Z DEBUG ThreadId(01) livetwo::whep: livetwo/src/whep.rs:96: Codec Info CodecInfo { video_codec: None, audio_codec: None }
2025-01-06T07:24:19.171384Z  INFO ThreadId(01) livetwo::whep: livetwo/src/whep.rs:106: SDP: "v=0\r\no=- 183888296887058999 136942000 IN IP4 0.0.0.0\r\ns=-\r\nt=0 0\r\n"
2025-01-06T07:24:19.171573Z  INFO ThreadId(01) livetwo::rtspclient: livetwo/src/rtspclient.rs:437: Connecting to RTSP server at localhost:8554
2025-01-06T07:24:19.175235Z DEBUG ThreadId(01) livetwo::rtspclient: livetwo/src/rtspclient.rs:466: track video: None, audio: None
thread 'main' panicked at src/whepfrom.rs:51:6:
called `Result::unwrap()` on an `Err` value: No tracks found in SDP
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Maybe SDP has some problem

What service did you use to verify this feature?