ITL: Network Protocol for all Manubulon SNMP Checks

[oxzi]

Add a new snmp_network_protocol custom var to all Manubulon SNMP checks to configure the underlying network protocols. By default, the snmp-manubulon-command template, used by all Manubulon SNMP checks, sets the protocol to udp and the version of the IP matching the snmp_address.

In the meantime, the upstream moved to GitHub. This was also reflected in the docs and outdated comments, pointing to outdated versions of the checks, were removed.

---

I have tested these changes with the following four hosts.

template Host "snmp-test" {
  import "generic-host"
  vars.snmp_test = true
}

object Host "snmp-test-v4only" {
  import "snmp-test"
  address = "127.0.0.1"
}

object Host "snmp-test-v6only" {
  import "snmp-test"
  address6 = "::1"
}

object Host "snmp-test-ds-v4" {
  import "snmp-test"
  address = "127.0.0.1"
  address6 = "::1"
  vars.check_ipv4 = true
}

object Host "snmp-test-ds-v6" {
  import "snmp-test"
  address = "127.0.0.1"
  address6 = "::1"
  vars.check_ipv6 = true
}

apply Service "snmp-interface" {
  import "generic-service"

  check_command = "snmp-interface"

  assign where host.vars.snmp_test
}

The --protocol flag of the executed command contained either udp/ipv4 or udp/ipv6, matching the expectation reflected in the host name.

---

Fixes #10790.

[oxzi]

Just saw that the upstream added this flag in two batches:

1. SteScho/manubulon-snmp@5369da5 in 2013 for only a few plugins, part of release v2.0.0.
2. SteScho/manubulon-snmp@394ade3 in 2024 for the remaining plugins, part of no official release.

I am unsure if my changes would be breaking, e.g., for users of an older version of the plugin. In general, the project seems to became quite slow in the last decade.