core: camera-manager: add "Disable MAVLink" option

[ES-Alexander]

Current behaviour

Currently every detected camera is presented by BlueOS via MAVLink, but users may wish for some (or all) connected camera streams to only be presented via non-MAVLink-enabled applications.

This forum post brings up one such use-case, which is compounded by QGroundControl automatically streaming at least one MAVLink-enabled stream (if one is available), which then prevents other applications from accessing that stream. Presumably a workaround would be to add a second stream endpoint for a camera, but that seems both unnecessary and unintuitive to need to do, and may be difficult to manage which endpoint is being used for/via MAVLink.

Edit: an additional workaround would be to ensure any external streams are connected to before a MAVLink-camera-enabled application is opened, which avoids adding unnecessary redundancy but is still not intuitive or user-friendly.

Expected or desired behaviour

In order of preference

1. A "Disable MAVLink" option per endpoint of each camera
   • neat/intuitive UI may be tricky, but this is the best for functionality
   • preferably something like a checkbox beside each endpoint, but effective labelling may be tricky
   • if necessary could even be added in the "Extra configuration" dropdown as an input for a comma-separated list of indices
2. A "Disable MAVLink" checkbox per camera
   • e.g. in the existing "Extra configuration" dropdown
3. A "Disable MAVLink" checkbox for the entire camera manager
   • seems much less versatile than the alternatives, but would at least solve the use-case in the forum post

This is advanced configuration, so should only be available in Pirate mode.

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.

[ES-Alexander]

@joaoantoniocardoso has mentioned that

another workaround, if no video streams are being used on qgc, is to start mavlink-camera-manager with an unreachable mavlink ip/port. ... it can be done inside the terminal, by killing (ctrl+c) the mavlink-camera-manager on the video terminal, and then starting it again but changing the ip address to something unreachable like 127.1.1.1

That approach avoids configuration of the topside computer, and of the stream, but I'm not sure if it would be persistent across restarts. That may require changing the default port or IP in a file somewhere, which could potentially be ill-advised.