Adds support for Zenmuse XT Thermal images

[pierotofy]

Adds support for Zenmuse XT thermal images (with radiometric calibration).

[pierotofy]

@holyCowMp3 while I was making these changes I noticed that https://github.com/OpenDroneMap/ODM/blob/master/opendm/thermal_tools/dji_unpack.py#L16 has the meta vars hard-coded, I don't have test images from an enterprise mavic 2 so I'm leaving them there, but note that we now have functions to extract those values (extract_raw_thermal_image_data). Perhaps even remove/condensate the Pillow code that unpacks the raw thermal image, since the exiftool function I wrote in this PR should be able to handle them.

If you have a dataset to share I can run some tests and update the code accordingly.

[sbonaime]

@pierotofy Do you think thermal images from Zenmuse XT2 could be use with this commit ? How can I check ?
Thanks

[pierotofy]

Maybe, try it out and see if you get reasonable values.