Firewall rules should allow setting/viewing multiple ICMP filters

[FelixMcFelix]

VpcFirewallRuleProtocols can now carry more information than a protocol alone. Today this is only expressed in ICMP type/code filters, but in future this will include ICMPv6 and probably a generic selector over the IP protocol code. We should allow interaction with a list of filters, rather than the three checkboxes we have today.

https://github.com/oxidecomputer/omicron/blob/d84882702969e42be311f1b4274ab9a4ab9d28a3/openapi/nexus.json#L26196-L26251

The move from representing each as a string to a kind+value will also impact how these are serialised/deserialised.

[david-crespo]

Confirmed these changes manifest as type errors when we bump the API client: