Clean up onvif and autotracking (#24559)

* simplify onvif and autotracking code

Removes about 230 lines from the ONVIF controller and autotracker without changing how PTZ moves are calculated. `OnvifController` no longer keeps its own `camera_configs` copy of the camera config, the cached `GetStatus`, `GetServiceCapabilities`, and `AbsoluteMove` request objects are gone in favor of plain dicts at the call site, and `PtzAutoTrackerThread` is merged into `PtzAutoTracker`. Repeated blocks in the autotracker (waiting for the motor to stop, disabling autotracking on a failed setup step) are now single helpers.

* use camera config for autotracking enabled state

Camera processes read autotracking state from a shared `autotracker_enabled` value that the dispatcher and autotracker had to keep in sync with the config by hand. Camera processes now subscribe to the `autotracking` and `onvif` config updates and read `onvif.autotracking.enabled` directly, so the shared value and the autotracker's mirroring method are gone. `_disable` now publishes its change so the camera process hears about it. Also removes `tracking_active`, which was set and cleared but never read.

* compute max target box from live zoom factor

* fix autotracking debug overlay max target box lookup

* make max target box a function of zoom factor

frigate/camera/maintainer.py

@@ -120,9 +120,7 @@ class CameraMaintainer(threading.Thread):
 
         if runtime:
             self.camera_metrics[name] = CameraMetrics(self.metrics_manager)
-            self.ptz_metrics[name] = PTZMetrics(
-                autotracker_enabled=config.onvif.autotracking.enabled
-            )
+            self.ptz_metrics[name] = PTZMetrics()
             self.region_grids[name] = get_camera_regions_grid(
                 name,
                 config.detect,