This commit enables FTS via Xapian, and exposes the port required for
ManagedSieve integration with Dovecot; additionally, bugs in the
integration of LMTP with RSpamd have been fixed.
In support of these changes, configuration files that were previously
split into container-based and service-based are now consolidated, and
we now ensure that only our own container-based configuration is used
when running Dovecot.