(cherry picked from commit e342cd97)

(cherry picked from commit a9fa3d52)

Lookie how far we've come...

(cherry picked from commit 6ee8eb78)

(cherry picked from commit 48c5641f)

(cherry picked from commit 21418708)

(cherry picked from commit a8962f5e)

(cherry picked from commit 6374e846)

(cherry picked from commit 08c1e186)

(legacy) change behaviour of associated nat rules (https://github.com/opnsense/core/issues/695), show rule but hide edit and duplicate buttons

If for some reason a config has "typeless" rules, which don't belong to any active nat rule the user won't notice this anymore (and doesn't have the ability to remove them).
This can happen with imports from old configs for example or manually changed configs.

(cherry picked from commit e1dd1839)

Closes #726

(cherry picked from commit 26a8f686)

(cherry picked from commit 0f0a1959)

(cherry picked from commit bb2be712)

(cherry picked from commit f53146b3)

There are a few cases where the gateway code is eligible
to drop a gateway on grounds of being disabled, inactive,
unconfigured or where the actual interface assigned is
disabled.  This is undesire because users that configure
a gateway won't be able to use it.

There are no bad side effects from the former by selecting
a whatsoever dysfunctional gateway, because the problem still
has to be fixed by the user in the gateway setup itself.

Worst of all, removing a disabled but used gateway makes
it not show up on edit, effectively wiping its setting on
save.  This breaks POLA.

While there, also enable the null routes for IPv4 and IPv6.

PR: https://forum.opnsense.org/index.php?topic=2100
(cherry picked from commit 2db592b1)

(cherry picked from commit 7fb658c1)

(cherry picked from commit 27a4c795)

(cherry picked from commit 4c5a093b)

(cherry picked from commit c0d4c4be)

(cherry picked from commit a3b63565)

(cherry picked from commit 1aedcd49)

(cherry picked from commit 9910a79f)

(cherry picked from commit 551289a5)

(cherry picked from commit 32c774fb)

(cherry picked from commit d61fb7f9)

(cherry picked from commit 8a309525)

(cherry picked from commit 3592b64f)

(cherry picked from commit 06795584)

(cherry picked from commit aa0fc181)

(cherry picked from commit 315d3371)

PR: https://forum.opnsense.org/index.php?topic=2012.0
(cherry picked from commit 9dd8a244)

(cherry picked from commit 23ef5f70)

(cherry picked from commit f903f986)

(cherry picked from commit 31952088)

(legacy) unbound renders some illegal output for empty ipv6, closes https://github.com/opnsense/core/issues/738

(cherry picked from commit ebd02c22)

(cherry picked from commit 555fda69)

(cherry picked from commit 95fb0aa3)

(cherry picked from commit 0201f60b)

(cherry picked from commit 4fc39576)

(cherry picked from commit e6ee8423)