bug: camera manager not presenting cameras correctly over MAVLink

### Bug description

QGroundControl allows switching between the camera streams it receives information about via MAVLink, but there seems to have been a regression in the camera manager that no longer supports that functionality.

### Steps to reproduce

1. Install `BlueOS-1.1.1` on a system with multiple video streams
2. Open QGroundControl
3. Set a joystick button function to "Next Camera" or "Previous Camera"
4. Pressing the button while in Fly View switches the camera feed, as expected
- From the release notes, this seems to use MCM `t3.12.1` ✅
5. Install `BlueOS-1.2.0-beta.1` (or any more recent version)
6. Joystick switching no longer works
- MCM >= `t3.12.4` ❌

### Primary pain point(s)

Users can't switch camera streams in QGC (and other applications/programs using the same mechanism), which wastes their additional camera hardware and bandwidth usage.

### Additional context

First raised in [this forum thread](https://discuss.bluerobotics.com/t/how-do-you-use-2-cameras-on-qgroundcontrol/2533/28).

### Prerequisites

- [X] I have checked to make sure that a similar request has not already been filed or fixed.