add ICMP type to firewall rules support

[Ian Booth]

Juju supports adding ICMP firewall rules, but does not support specifying the ICMP type.

It seems libs like gopkg.in/amz.v4 lack this support in their APIs, so we'd need to audit and update those cloud API libraries if necessary in order to add support to Juju.

Getting this done is important as it's a potential security hole not to be able to have it if we want charms to use it.

At the very least, we should extend the open-port/close-port syntax to support the icmp type even if we don't yet implement it.

[Ian Booth (wallyworld)]

This isn't critical since not all clouds seem to support ICMP type rules eg AWS does but not Azure

[Canonical Juju QA Bot (juju-qa-bot)]

This bug has not been updated in 2 years, so we're marking it Low importance. If you believe this is incorrect, please update the importance.