Allow KustomizationRef.Path and PolicyRef.Path to be template

[gianlucam76]

This allow Sveltos to decide which path to use at run-time.

For instance, this repo https://github.com/gianlucam76/kustomize has two directories with kustomize files:

1. production
2. pre-production

The only difference between the two is that Deployment in production/helloWorld has replicas set to 3, while the Deployment in pre-production/helloWorld has replicase set to 1.

By creating this ClusterProfile:

apiVersion: config.projectsveltos.io/v1alpha1
kind: ClusterProfile
metadata:
  name: flux-system
spec:
  clusterSelector: region=west
  syncMode: Continuous
  kustomizationRefs:
  - namespace: flux-system
    name: flux-system
    kind: GitRepository
    path: '{{ index .Cluster.metadata.annotations "environment" }}/helloWorld'
    targetNamespace: eng

For every matching cluster, Sveltos will first instantiate the path so:

1. picking production/helloWorld path if cluster has annotation environment: production
2. picking pre-production/helloWorld path if cluster has annotation environment: pre-production

Closes #532
Closes 278