AP_Camera/AP_Mount/GCS_MAVLink: Siyi implements camera-thermal-range

[rmackay9]

This PR adds support for sending the min and max temperatures and their XY positions in the live video stream to the ground station when using Siyi ZT6 and ZT30 cameras. We can add support for ViewPro and Topotek cameras in a follow-up PRs.

This is useful for search & rescue and firefighting applications because the ground station can overlay a rectangle over the hotspot along with its temperature.

This PR relies on this mavlink PR ArduPilot/mavlink#369 (and the equivalent upstream PR mavlink/mavlink#2145).

It is also built on PR #27890 and PR #27911 so those should be merged first.

This has been lightly tested on real-hardware (a CubeOrange + Siyi ZT6) and below is a screen shot showing the temperature jump when I moved in front of the camera although please note that the test used named value pairs to send the temperatures and positions instead of using the new mavlink message.

[rmackay9]

This has been updated inline with discussion on the upstream mavlink PR mavlink/mavlink#2145

[rmackay9]

I've updated this to use the final CAMERA_THERMAL_RANGE mavlink message definition and also hidden the feature behind a define

Currently the new message is only sent if requested by the GCS (e.g. not sent by default)

[peterbarker]

LGTM past these

[rmackay9]

feature size info

Binary Name      Text [B]        Data [B]     BSS (B)        Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  --------------  -----------  -------------  ----------------------------  -------------------------
arducopter       692 (+0.0384%)  0 (0.0000%)  4 (+0.0015%)   692 (+0.0384%)                                   161192
antennatracker   108 (+0.0081%)  0 (0.0000%)  4 (+0.0015%)   108 (+0.0081%)                                   631524
arducopter-heli  692 (+0.0385%)  0 (0.0000%)  -4 (-0.0015%)  692 (+0.0384%)                                   162160
ardusub          692 (+0.0435%)  0 (0.0000%)  -4 (-0.0015%)  692 (+0.0434%)                                   370788
ardurover        688 (+0.0417%)  0 (0.0000%)  0 (0.0000%)    688 (+0.0416%)                                   312848
blimp            112 (+0.0083%)  0 (0.0000%)  0 (0.0000%)    112 (+0.0083%)                                   609312
arduplane        696 (+0.0387%)  0 (0.0000%)  0 (0.0000%)    696 (+0.0386%)                                   164248

PeterB's requests implemented, txs for the review!