[3007.x] Fix/add nftables icmpv6 support

[jdelic]

What does this PR do?

Fixes #67882

The nftables state just sends its kwargs to the nftables module. This in turn is currently missing support for ipv6 icmp packet types (icmpv6). This means that currently Salt cannot configure a firewall in such a way that it allows pings, for example. This small patch remedies that.

Previous Behavior

The following was impossible:

icmp-recv-ipv4:
    nftables.append:
        - table: filter
        - family: ip4
        - chain: input
        - jump: accept
        - proto: icmp
        - icmp-type: echo-reply,destination-unreachable,source-quench,redirect,echo-request,time-exceeded,parameter-problem,timestamp-request,timestamp-reply,info-request,info-reply,address-mask-request,address-mask-reply,router-advertisement,router-solicitation
        - order: 4
        - save: True
        - require:
            - pkg: nftables


icmp-recv-ipv6:
    nftables.append:
        - table: filter
        - family: ip6
        - chain: input
        - jump: accept
        - proto: icmp
        # This wasn't supported until now --v
        - icmpv6-type: echo-reply,echo-request,nd-router-advert,nd-neighbor-solicit,nd-neighbor-advert
        - order: 4
        - save: True
        - require:
              - pkg: nftables

New Behavior

The above works now.

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

I have not added any test for the above.

1. The current icmp-type functionality is untested
2. The current tests don't really test anything. They test that the module returns a state comment which fits the expectation and mock cmd.run. So nft is never executed by the tests, so you'd never know if any of this code produced an invalid rule. I do not have the time to contribute to Salt to essentially rewrite the nftables module, so this will have to live without tests.
3. The current documentation isn't really explaining the list of available parameters from the module. Neither does the module. Both need improvement, as do the tests, but this PR is about simply adding support for icmpv6.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

[twangboy]

Please write a test for this

[jdelic]

Please write a test for this

I explained in the PR description why I didn't. That argument still stands.

[dmurphy18]

@jdelic Regardless of opinions, if you change code, you write a test to check that code, unless there is already a test which covers the change. This rule applies to the core team too.
Just because some test doesn't already exist is no excuse to not write a test.

In the past, before 2019, Salt would allow code to be merged after code review without tests been written for it, and this led to a mess, hence since 2019, all code changes require tests, and tests using pytest. Using mock can test the code without having to have an actual VM up etc., noting even simple unnoticed typo's parsing a kwarg can trip code up.

Tests have been written