Polling on instance list

Closes #2377

[x] Smart logic
[x] e2e test it
[x] Figure out how to indicate when we're polling (don't. use "Updated" message)

Demo

When the page loads below, it polls every 3 seconds because there is an instance in a starting state. After 30 seconds, it would switch to polling every minute, but I don't wait for that in this clip. I stop the instance, which causes it to transition to stopping, and the stopped (because of the polling). At that point, there are no instances in transitional states, so polling slows to every minute (i.e., not at all in the short time in this clip). Then when I start the instance it polls again while it's in starting and then stops (slows) again after it's running.

https://github.com/user-attachments/assets/3328ec0f-ceef-4b93-bad1-77d5b1eb5d05

oxidecomputer / console

Polling on instance list #2391

Demo