Add managed firewall support for VKE

[Byteflux]

Description

Adds managed firewall support for VKE clusters:

• enable_firewall can be used as an argument to create clusters with a managed firewall.
• The ID of the managed firewall is exposed in the firewall_group_id attribute.

Checklist:

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

[optik-aper]

Looks good