`disaggregate_to` rules result in console spam

[irm-codebase]

This mostly affects snakemake or scripts that display console messages (e.g., Jupyter notebooks).

There are a bunch of print messages in the disaggregate code, which results in spam that is easily missed by users.
I suggest using warn instead, as most of these messages relate to (potentially) problematic execution.
print reaches the console, but warn reaches stderr which is where most applications expect warnings to be in.

Otherwise, INFO level logging might suffice.