Cluster generator cannot select local cluster

[jgwest]

This PR switches the behaviour of the cluster generator, such that it will now target both local AND non-local clusters (eg those with secrets defined).

If you wish to use the existing behaviour -- that is, targeting non-local clusters only with your Application -- then use a cluster selector with labels, for example:

  generators:
  - clusters:
      selector:
        matchLabels:
          argocd.argoproj.io/secret-type: cluster

This selector will not match local clusters, since the local cluster does not have a secret (and thus does not have labels on that secret). Any cluster selector that specifies on a label will automatically exclude local clusters.

If you wish to target both local and non-local cluster, using labels, you can create a secret for the local cluster as per the parent issue.

I'm using the existing Argo CD util/db package logic (pulled in directly from that package) to identify local/non-local clusters.

Additional tweaks

Clean up cluster unit tests

• add test names
• remove base64 encoding on Data field (it should be decoded)
• general cleanup (add fields to test struct)

Clean up cluster E2E tests:

• move cluster e2e tests into their file
• miscellaneous test fixture tweaks

Fixes #35