Reduce exposed code

[leggsimon]

@jkerr321 has done some checking around to see whether we could deprecate some of the exposed functions in this repo.

Currently there are 11 modules exposed, of these, userProfileClient isn't used anywhere (except kat-nip which I believe is a deprecated repo.)

elacticsearchClient and facetsClient are only used by kat-api so could potentially be moved there.

Likewise, syncUserFollows is only used by kat-myft-syncher so this could possibly be moved there.

Ultimately, I don't mind where things go but we need to decide what this module is providing rather than it just being a dumping ground for unrelated things