Add clerk/resolve-aliases and make alias resolution explicit

[mk]

This makes the alias resolution explicit via a new clerk/resolve-aliases function. The recommendation is now to use the full namespace in :render-fns or make the conversion explicit using clerk/resolve-aliases.

I've also removed the automatic resolution from ->viewer-fn/eval because it would depend on the evaluation context (a notebook that defines a viewer using aliases would render correctly but things could break if that viewer is being reused from another namespace that doesn't define the same aliases).

Lastly we've dropped the previously defined aliases:

{'j 'applied-science.js-interop
 'reagent 'reagent.core
 'v 'nextjournal.clerk.viewer
 'p 'nextjournal.clerk.parser}

We should think about temporarily bringing them back and log a warning instead before the next release, so folks have time to migrate but I'd like to make sure all our notebooks aren't using them anymore.