Move pouchdb-collate and pouchdb-collections into core

[nolanlawson]

With the new monorepo setup, this should be a slam-dunk. There's no reason to have these as a separate repo.

BTW I found this awesome Lerna tool that can import a separate Git repo with version history! Thanks @hzoo. :)

[nlfiedler]

Are the functions from pouchdb-collate exposed in pouchdb core now? The other module is deprecated, but I can't find how to use this API within PouchDB 6.3.4. I see the functions in the code, but they are not exposed? Guides and API docs don't talk about it either.

[daleharvey]

They are in the pouchdb repo to be used by pouchdb core, but they are not part of the pouchdb core api, if you want to use them you need to do so directly, closing since they are in the repo