refactor: Unify substream actions into substream_{on,off} (#2497)

## Summary

- Collapse `live_substream_{on,off,select}` into a unified
`substream_{on,off}` pair, symmetric with `call_{start,end}`.
- Rename the `camera` field on the former `live_substream_select` to
`stream` (it always was a stream ID).
- Add optional `camera` field to both new actions for targeting a
non-selected base camera.
- YAML configs are migrated automatically; URL bookmarks must be updated
by hand.

## Migration

### Cycling between camera and substream (toggle button)

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_on
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_on
```

### Selecting a specific substream

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_select
  camera: camera.front_door_hd
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_on
  stream: camera.front_door_hd
```

### Turning the substream off

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_off
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_off
```

### URL querystrings (manual update required)

| Before | After |
| --- | --- |
|
`?advanced-camera-card-action.live_substream_select=camera.front_door_hd`
| `?advanced-camera-card-action.substream_on=camera.front_door_hd` |

src/card-controller/call/manager.ts

@@ -134,7 +134,7 @@ export class CallManager {
       ...(needsNavigation && {
         params: { view: 'live', camera: parentID },
       }),
-      modifiers: [new SubstreamViewModifier(callCameraID, parentID)],
+      modifiers: [new SubstreamViewModifier({ stream: callCameraID, camera: parentID })],
       force: true,
     });
     this._api.getConditionStateManager().setState({ call: true });
@@ -255,12 +255,11 @@ export class CallManager {
       const previousStream = getStreamCameraID(previousView, call.cameraID);
       viewManager.setViewByParameters({
         modifiers: [
-          new SubstreamViewModifier(
-            previousStream && previousStream !== call.cameraID
-              ? previousStream
-              : undefined,
-            call.cameraID,
-          ),
+          new SubstreamViewModifier({
+            ...(previousStream &&
+              previousStream !== call.cameraID && { stream: previousStream }),
+            camera: call.cameraID,
+          }),
         ],
         force: true,
       });