Add a way to get RTSP status

[PulpFiction-Jeson]

1.Add a way to get RTSP status
2.Reset the state when you actively call Stop()

Reason for change：
When doing real-time preview and switching of multiple streams, you can create and reuse RTSPClient instances in advance. Call connect when you need to play, and call stop when you don't. Before calling, you can use rtspstatus to check the status of the current instance to avoid repeated calls and some errors.

[Copilot]

Pull request overview

This PR adds a public way to query an RTSPClient instance’s RTSP connection status and resets the internal status state when Stop() is called, supporting scenarios where a client instance is reused across multiple stream switches.

Changes:

• Exposes RtspStatus publicly and adds a public API to retrieve the current status.
• Resets _rtspSocketStatus to WaitingToConnect when Stop() is called.

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[PulpFiction-Jeson]

In my project, there are many plans (a plan represents which streams are shown on several monitors, or something similar). For each stream, I create an RTSP client instance, each with its own thread, constantly checking whether the stream needs to connect() or stop(). Without this status, there's no way to tell.