Update elevation extraction logic to first extract the data axis to CRS axis mapping from DEMs

[spwoodcock]

Feedback from #590

• @andrewharvey reported that the X/Y axis were flipped in their output running drone-flightplan manually, with a custom DEM.
• Originally we thought it was an issue with GDAL after version upgrades, but we have since also upgraded to Debian Trixie (13) and GDAL 3.10.3 without issues.
• The likely problem is in the DEM we are using - the JAXA DEMs probably have a flipped [data axis to CRS axis mapping](DEM files report a different Data axis to CRS axis mapping? In that case we probably need to detect this when reading the DEM file.) (original comment: "DEM files report a different Data axis to CRS axis mapping? In that case we probably need to detect this when reading the DEM file.").
• This is not a problem for the standard workflow using JAXA, but we need to account for the different types of DEMs users may upload themselves.

[linear]

TECH-957