Don't build full initial logical decoding snapshot if NOEXPORT_SNAPSHOT.
Earlier commits (
56e19d938dd14 and
2bef06d5164) make it cheaper to
create a logical slot if not exporting the initial snapshot. If
NOEXPORT_SNAPSHOT is specified, we can skip the overhead, not just
when creating a slot via sql (which can't export snapshots). As
NOEXPORT_SNAPSHOT has only recently been introduced, this shouldn't be
backpatched.