Dynamically enable/disable cameras (#16894)

* config options

* metrics

* stop and restart ffmpeg processes

* dispatcher

* frontend websocket

* buttons for testing

* don't recreate log pipe

* add/remove cam from birdseye when enabling/disabling

* end all objects and send empty camera activity

* enable/disable switch in ui

* disable buttons when camera is disabled

* use enabled_in_config for some frontend checks

* tweaks

* handle settings pane with disabled cameras

* frontend tweaks

* change to debug log

* mqtt docs

* tweak

* ensure all ffmpeg processes are initially started

* clean up

* use zmq

* remove camera metrics

* remove camera metrics

* tweaks

* frontend tweaks

web/src/components/camera/ResizingCameraImage.tsx

@@ -108,9 +108,7 @@ export default function CameraImage({
           width={scaledWidth}
         />
       ) : (
-        <div className="pt-6 text-center">
-          Camera is disabled in config, no stream or snapshot available!
-        </div>
+        <div className="pt-6 text-center">Camera is disabled.</div>
       )}
       {!hasLoaded && enabled ? (
         <div