Add rtsptowebrtc integration (#59660)

* Add initial version of the webrtc integration

Add the webrtc integration. This integration proxies the
signal 'offer' from the client to a RTSPtoWebRTCP server that
returns an 'answer'.

The RTSPtoWebRTC server is a go binary based on pion, and this is
what is currently used by the WebRTC custom_component:
https://github.com/AlexxIT/WebRTC
https://github.com/deepch/RTSPtoWebRTC

* Readability improvements for webrtc

* Reach 100% test coverage

* Use rtsp-to-webrtc client library package

* Rename webrtc to rtstptowebrtc

This is to reflect naming as one type of approach to webrtc since other webrtc integrations would look very different.

* Remove internal quality scale

* Bump rtsptowebrtc to support heartbeats

* Shorten server url variable and remove const.py

* Add config flow validation for RTSPtoWebRTC server

* Add RTSPtoWebRTC server health checks

* Accept translation suggestion

* Apply suggestions from code review

Co-authored-by: J. Nick Koston <nick@koston.org>

* Update rtsptowebrtc to use new camera registry API

Update rtsptowebrtc to use new API added in #62962

* Remove unused variable

* Fix lint and typing errors for python 3.8

* Rename to rtsp_to_webrtc to follow standards

* Use async_on_unload for unsubscribing camera webrtc provider

* Remove unnecessary translations in config flow

* Remove unnecessary configuration setup

* Cleanup test setup and typing

* Patch integration setup to avoid starting the whole integration

Co-authored-by: J. Nick Koston <nick@koston.org>

homeassistant/generated/config_flows.py

@@ -262,6 +262,7 @@ FLOWS = [
     "roomba",
     "roon",
     "rpi_power",
+    "rtsp_to_webrtc",
     "ruckus_unleashed",
     "samsungtv",
     "screenlogic",