Speed up loading of many tags on an item

[dstillman]

https://forums.zotero.org/discussion/93337/report-id-579048989

Currently, Tag::load(), which calls Tags::getPrimaryDataByID() and triggers a SELECT query, is run for every single tag.

Probably just as part of removing tags as first-class objects, with the removal of ClassicDataObjects

(170,000 tags is a bit of an edge case, though.)