CLI : prepare datas without coreg

[adebardo]

Context

Currently, in the CLI, the data are reprojected and intersected only when the user enables coregistration. However, it may happen that the user does not want to go through this step.

Code

We propose to make this function conditional not only for coregistration, but always.
https://github.com/GlacioHack/xdem/blob/main/xdem/workflows/accuracy.py#L141

Tests

Add unit tests.

Documentation

Update the documentation.