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` |

tests/components-lib/menu-button-controller.test.ts

@@ -278,7 +278,7 @@ describe('MenuButtonController', () => {
         type: 'custom:advanced-camera-card-menu-icon',
         tap_action: {
           action: 'fire-dom-event',
-          advanced_camera_card_action: 'live_substream_on',
+          advanced_camera_card_action: 'substream_on',
         },
       });
     });
@@ -322,7 +322,7 @@ describe('MenuButtonController', () => {
         type: 'custom:advanced-camera-card-menu-icon',
         tap_action: {
           action: 'fire-dom-event',
-          advanced_camera_card_action: 'live_substream_off',
+          advanced_camera_card_action: 'substream_off',
         },
       });
     });
@@ -394,8 +394,8 @@ describe('MenuButtonController', () => {
             selected: true,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-1',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-1',
             },
           },
           {
@@ -407,8 +407,8 @@ describe('MenuButtonController', () => {
             selected: false,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-2',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-2',
             },
           },
           {
@@ -420,8 +420,8 @@ describe('MenuButtonController', () => {
             selected: false,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-3',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-3',
             },
           },
         ],
@@ -489,8 +489,8 @@ describe('MenuButtonController', () => {
             selected: false,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-1',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-1',
             },
           },
           {
@@ -504,8 +504,8 @@ describe('MenuButtonController', () => {
             selected: true,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-2',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-2',
             },
           },
           {
@@ -517,8 +517,8 @@ describe('MenuButtonController', () => {
             selected: false,
             tap_action: {
               action: 'fire-dom-event',
-              advanced_camera_card_action: 'live_substream_select',
-              camera: 'camera-3',
+              advanced_camera_card_action: 'substream_on',
+              stream: 'camera-3',
             },
           },
         ],