Factor out common zarrification functionalities

[remicousin]

          > If/when you're ready to make a shared zarrification library, you can put it in the top level of this repo alongside `pingrid` and `controls.py`, and symlink it into the subdirectories that use it. E.g. `enacts/pingrid` is a symlink to `../pingrid`.

By the way, let's try to make sure all new zarrification scripts preserve or add appropriate CF standard_name metadata from now on.

Will make it a common library outside of this PR, just for the sake of time and to have a zarr version asap for Sheen to work on it. But will try to do it sooner than later so that we don't linker with two versions meant to be the same.

Can you give an example of the CF conventions preservation/additions? or how/what to check exactly? or a workflow to run that check?

Originally posted by @remicousin in #425 (comment)