Support loading swapped-axes image cubes (eg RA-Channel-Dec) (backend)

[kswang1029]

user feedback from v3 beta test

This is to support rotated cubes such as RA-Channel-Dec.

The backend needs to be able to recognize such cubes and generate proper file info.

The companion frontend issue is CARTAvis/carta-frontend#1953

[markccchiang]

@kswang1029 Do we have the sample file of the rotating cube to do the test?

[markccchiang]

@kswang1029 Is it OK to load a swapped-axes cube and render it as ra-dec image for now? The backend needs to tell the frontend real axis numbers of ra, dec, spectral, and stokes axes. So the frontend can render a ra-dec image with the correct coordinate system (in AST setting). I have created a backend branch mark/1178_support_swapped_axes_images and a frontend branch mark/support_swapped_axes_images for this task. While the region spectral profile, PV, and moments images need to fix too. Because the default ra and dec axis numbers are 0 and 1 in the backend. Considering to create another backend issue to fix it. To render a rotating cube as ra-channel or dec-channel images would be another issue too after the previous job is done.

[kswang1029]

@kswang1029 Is it OK to load a swapped-axes cube and render it as ra-dec image for now? The backend needs to tell the frontend real axis numbers of ra, dec, spectral, and stokes axes. So the frontend can render a ra-dec image with the correct coordinate system (in AST setting). I have created a backend branch mark/1178_support_swapped_axes_images and a frontend branch mark/support_swapped_axes_images for this task. While the region spectral profile, PV, and moments images need to fix too. Because the default ra and dec axis numbers are 0 and 1 in the backend. Considering to create another backend issue to fix it. To render a rotating cube as ra-channel or dec-channel images would be another issue too after the previous job is done.

The main goal is to let the backend load a cube with the axes in any order and let the frontend render the first two axes as x and y and being able to animate in z.

[kswang1029]

done via #1194