Spaces: add support for public load balancer

[darkmuggle]

Description of your changes

• Improve detection of Kubernetes providers for Spaces
• Provision public LB on managed Kubernetes

I have:

• [x] Read and followed Upbound's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] Added backport release-x.y labels to auto-backport this PR, as appropriate.

[darkmuggle]

Tested and confirmed to work with GKE, AKS, EKS and kind -- all work beautifully