Add node-pool list summarize flag

[optik-aper]

Description

I thought this would be useful for quick glance node pool list, like what we use for the kubernetes clusters

Testing

go run main.go kubernetes node-pools <UUID> --summarize

Checklist:

• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you linted your code locally prior to submission?
• [x] Have you successfully ran tests with your changes locally?

[github-actions[bot]]

Unit Tests and Coverage

Show Output

?   	github.com/vultr/vultr-cli/v3	[no test files]

Pusher: @optik-aper, Action: pull_request_target

[github-actions[bot]]

Unit Tests and Coverage

Show Output

?   	github.com/vultr/vultr-cli/v3	[no test files]

Pusher: @optik-aper, Action: pull_request_target