Try-restart networkd, resolved, and timesyncd after an upgrade.

Just like is already done for journald and logind.
Do not force-enable default-on services on every upgrade.

Also drops the systemd-networkd, systemd-resolved and systemd-timesyncd
from the set of default services, but restarts them during an upgrade
if they were already running.
Add support for rcS.d init scripts to the sysv-generator.
Do not order rcS.d services after local-fs.target if they do not explicitly depend on $local_fs.
Map init script dependencies on cryptdisks, mountall, and mountnfs to the corresponding systemd targets.
Prevent rcS.d services from depending on remote-fs.target or network-online.target.
Order rcS.d init scripts before basic.target instead of sysinit.target.
Add breaks on old syslog providers, they interact badly with the journal.
Add breaks on old resolvconf, it interacts badly with systemd-resolved.
Bump dependency on sysv-rc to 55.3 for an update-rc.d that does not make assumptions broken by the sysv-generator.