Add "IPv4+IPv6" protocol value for IPSEC mobile VPN

[goodomens42]

• [ x] I have read the contributing guide lines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• [ x] I have searched the existing issues and I am convinced that mine is new.

IPv6 is becoming more important day by day as more and more mobile users are using connections with DS-Lite or pure IPv6.
In order to setup a mobile tunnel that works with IPv4 and IPv6 in OPNsense you have to specify the interface as "any".
This approach might have undesired side effects in a configuration with several WAN interfaces that are used for IPSEC.
It would be nice to have a "clean" way to configure the mobile user connection for both IPv4 and IPv6.

I have created a patch, that allows setting the protocol to "any" when editing the mobile user connection.
The generated StrongSwan configuration will then contain something like

left = 1.2.3.4,2001:1:2:3:4::1

which works fine for us in production use.
I am aware this will only work for IKEv2, maybe there should be some kind of warning if using protocol=any with IKEv1.

opnsense_ipsec.patch.txt

[AdSchellevis]

@goodomens42 we don't accept patches inside issues, for discussion and feature merges we advise to use the normal GitHub PR process (https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/about-pull-requests)

[jasperroloff]

@goodomens42 Based on your patch, I've created a PR: see #5166

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