Instead, don’t create the library at all if not needed.

fix #3360

fix #3359

If a user manually does a NAMES query, the result were interpreted as a user
list, which is wrong. And with the special * argument, this would even cause
a crash.

Fix #3357

fix #3356

Because that’s what is typically done on other deamons, and we don’t want to
suprise users.

fix #3351

See https://github.com/randombit/botan/issues/1558

Also simplify how we did the whole “limit + 1”
And fix one bad interpretation of the XEP for the case where the query has
no after or before restriction.

fix #3349

fix #3343

This reverts commit 857c7d39.

This reverts commit 5ef7ba08.

This way, it works, whatever the order of insertion in the database was.

fix #3343