Support validating Namespaces

[stevendborrelli]

What problem are you facing?

As part of testing a number of namespace-based claims, we create namespaces that uptest cannot validate:

    logger.go:42: 18:08:15 | case/0-apply | error: timed out waiting for the condition on namespaces/team-1

This is probably similar to #37

How could Uptest help solve your problem?

Uptest should know not to expect XP readiness checks on native Kubernetes resources.

[stevendborrelli]

It seems this should already work: https://github.com/upbound/uptest/blob/306a7e7e218a7a31bbd983fff7c2efb7f96bf8e6/internal/templates/00-assert.yaml.tmpl#L14