Remove cruft code, dependencies

[brews]

Removes unused code, commands from dodola.

More specifically, this removes dodola commands:

• dodola biascorrect
• dodola downscale
• dodola buildweight

Internally, this removes:

• dodola.core.apply_bias_correction
• dodola.core.apply_downscaling
• dodola.core.build_xesmf_weights_file
• dodola.services.bias_correct
• dodola.services.downscale
• dodola.services.build_weights

Relevant tests and external package dependencies (scikit-downscale) are also removed.

close #20
close #82

[brews]

For reviews, this is largely a heads-up. Please let me know if I'm removing something critical.

[emileten]

I was wondering whether we were using those at all. Thanks for the cleanup 👍