Don't force reprojection for all coreg method in the CLI accuracy workflow

[marinebcht]

Following #759 (comment) and #873 sampling_grid modif
ICP and CPD work even if datasets are not reprojected

• ICP method is not allow yet, check why
• allow sampling_grid: None when it is possible and test it
• verify for all method the behaviour of the coreg when dem1 and dem2 don't intersect each other

[rhugonnet]

Perfect! To-do once #759 is merged

[rhugonnet]

Note: Not reprojecting before coregistration should be the default (i.e., we mirror exactly what the Coreg module does).
We can still reproject before for the sake of deriving + plotting a "before dh map", but we don't pass that reprojected dataset to the coregistration (we keep the original).

[belletva]

Don't force reprojection also in xdem.coreg.BlockwiseCoreg see: #916