Firewall rules not updated for renamed VPC

Perhaps this should be in https://github.com/oxidecomputer/omicron but I experienced it in the web console so I'll file it here.

1. Create a VPC named k8s.
2. Observe the default allow-icmp firewall rule targets the k8s VPC.
3. Rename the k8s VPC to ms-k8s.
4. Observe the default allow-icmp firewall rule still targets the old k8s VPC.
5. Attempt to update the allow-icmp firewall rule.
   1. Delete the k8s VPC target.
   2. Add the ms-k8s VPC target.
   3. Click "Update Rule" and note the Cross-VPC firewall host filter unsupported error.
6. Refresh the VPC firewall rules list and note the allow-icmp rule was indeed updated with the ms-k8s VPC target.

Here's what the JavaScript console showed when I clicked "Update Rule".

API URL:        https://oxide.sys.r3.oxide-preview.com/v1/vpc-firewall-rules?project=matthewsanabria&vpc=ms-k8s
Request ID:     21647ed3-cef9-4b39-9068-c74fbe1d6925
Error code:     InvalidRequest
Error message:  Cross-VPC firewall host filter unsupported

I'd do more digging on this but I'm in the middle of a few things. I wanted to file the issue though so I didn't forget about it.

Start by tracing the VPC firewall-rules API request shown in the report and reproduce the rename and rule-update sequence. Inspect how the renamed VPC target is handled and verify that the allow-icmp rule points to the new name and can be updated without the Cross-VPC firewall host filter unsupported error.