rc.d: add a service jails config to all base system services

This gives more permissions to services (e.g. network access to
services which require this) when they are started as an automatic
service jail.

The sshd patch is important for the sshd-related functionality as
described in the man-page in the service jails part.

The location of the added env vars is supposed to allow overriding them
in rc.conf, and to hard-disable the use of svcj for some parts where it
doesn't make sense or will not work.

Only a subset of all of the services are fully tested (I'm running this
since more than a year with various services started as service jails).
The untested parts should be most of the time ok, in some edge-cases
more permissions are needed inside the service jail.
Differential Revision: https://reviews.freebsd.org/D40371

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

growfs_fstab startup script: set dumpdev to AUTO

The growfs_fstab script has been testing dumpdev, and if it is AUTO,
enables dumps on the newly-added swap device for the initial boot.
However, dumpdev defaults to AUTO on main, but NO on stable/13 and
release branches. On the other hand, bsdinstall adds dumpdev="AUTO"
by default (controlled by a menu item). bsdinstall is not used when
booting an SD card or other disk image. Adopt the default from
bsdinstall, and set dumpdev to AUTO in /etc/rc.conf in the
growfs_fstab script if a swap partition has been added, along with
the explanatory comment added by bsdinstall.

Differential Revision: https://reviews.freebsd.org/D38751

growfs_fstab: add new /etc/rc.d script to add swap to fstab

The growfs_fstab script is a helper for the growfs script to add any
new swap partition to /etc/fstab on first boot. If growfs adds a
swap partition, it sets growfs_swap_pdev in the kenv. In this case,
after the root file system is read/write, if there is no swap partition
in the fstab, growfs_fstab adds growfs_swap as a swap partition to the
fstab. Also, it runs dumpon to add the swap partition (as this
happened earlier in the startup sequence).

Discussed with: cperciva
Differential Revision: https://reviews.freebsd.org/D37463