AP_Camera, AP_Mount: Add handler for CAMERA_CAPTURE_STATUS request

[nexton-winjeel]

QGroundControl uses the CAMERA_CAPTURE_STATUS message to update the camera control UI. This PR adds support for this message to AP_Camera and AP_Mount.

FYI: @rmackay9, @peterbarker

[nexton-winjeel]

I have a second branch to add support for the CAMERA_CAPTURE_STATUS message to the Siyi driver, but it's blocked on #24808.

[nexton-winjeel]

I've copied the way the other messages (e.g. CAMERA_SETTINGS, CAMERA_INFORMATION) are handled.

However, these handlers are problematic if there are multiple camera backends:

• these messages do not have IDs (MAVLink intent is to use compid to distinguish components);
• however, all of these are sent with the MAV_COMP_ID_AUTOPILOT1 compid, which will confuse a GCS.

[nexton-winjeel]

Raised #24955.

[nexton-winjeel]

@rmackay9: Anything else you need for this PR?

[rmackay9]

It's just a style thing but maybe we can get rid of some of these intermediate variables and just directly place them in the "camera_capture_status_send(" section below? Then put the comments beside each field. "image_status" is the only one that is complex enough to be worth breaking out I think.

mavlink_msg_camera_capture_status_send(
    chan,
    AP_HAL::millis(),
    image_status,
    0,                                // current state of video capturing (0: idle, 1: capture in progress)
    time_interval_settings.time_interval_ms / 1000.0,  // Image capture interval (s)
    0,                                // time since recording started (ms)
    NaN,                           // available storage capacity (MiB), NaN if unknown
    image_index);             // total number of images captured

[nexton-winjeel]

Updated.

[rmackay9]

In any case, no need the the, "this->" I think.

[rmackay9]

@nexton-winjeel,

If you're happy making the mentioned style changes above then I think we can merge. You've tested this of course? I'm sure you have but just need to check.

[nexton-winjeel]

@rmackay9:

You've tested this of course? I'm sure you have but just need to check.

Yep, tested with a Siyi and QGC. I've got a follow-up branch that overrides send_camera_capture_status() in the Siyi driver to populate more fields.

[nexton-winjeel]

@rmackay9: Re. the Siyi updates: It's a single commit -- do you want it in this PR, or a separate one?

[rmackay9]

@nexton-winjeel,

Either is fine with me but maybe a follow-up PR would be better so we can merge this now.

[rmackay9]

Merged, thanks!