Align bands behavior: write them all on disk

[remi-braun]

It would be better to align all bands behaviors by writing the all on disk.

• spectral bands
  • ✔️written on disk
  • ✔queriable with get_band_paths
• DEM
  • ✔️written on disk
  • :x: not queriable with get_band_paths
• clouds
  • ✔️written on disk
  • :x: not queriable with get_band_paths
• spectral indices
  • :x: written on disk
  • :x: not queriable with get_band_paths

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    💡 It would also be nice to be able to retrieve them with get_band_paths ➡️ One big question though for get_band_paths alignement: should it compute the paths asked (copied on non-ortho bands) :x: I wouldn't do that right now, maybe it can be part of the issue #31

[remi-braun]

get_band_paths behavior will be dealt with elsewhere