Don't throw out field data; use cache for citeproc

[bdarcus]

Can you take a look at this @andras-simonyi @andersjohansson?

It's a simple solution to the problem we've previously discussed, and an alternative to #710. I mostly stole code from org-cite-csl-activate!

But this should:

1. fix citar-copy-reference slow? #702
2. provide all the advantages of using the citar cache
3. remove the potential limitation noted in the org-cite-csl-activate README.

The only problem I can potentially see is maybe it slows down initial loading of libraries a little, and uses a bit more memory. But I doubt it's a significant impact. And if it ever were, we could always add a defcustom so people could turn it off?

@andras-simonyi - not sure what you think about this, but one possibility is you can use the functions here instead, since you're already loading citar when available, and remove some code in org-cite-csl-activate in the process?

cc @benthamite

[bdarcus]

I can't see any downside to this, so have merged it!

[andersjohansson]

Got to this now and it seems to work well in my initial testing!

About performance:
For my 3.7 MiB json library file (exported from Zotero with BBT) I get very similar parsing times (4.5 s) when comparing before (97092df) and after (cb7d511) this change. I suppose this is reasonable since the parsing is the same only that some fields were discarded. memory-report gives 10 MiB versus 14 MiB for citar-cache--bibliographies. No big deal.

[bdarcus]

Great; thanks for the data!

BTW, you may also be interested in 82fdbae.