Add logging to collation-generation

Right now if the collation is not happening one will have to sprinkle
log statements and then recompile the code. It's doubly annoying if that
happens when working with Cumulus: that means one has to resort to
.cargo/config's `paths` or `diener`, which both are not ideal.

This just adds some verbose logging to save the investigators some time
when looking why the collations are not happening