collector: add set rewrites configurability

[alltilla]

Example to copy the time field from the kubernetes metadata to the top level

daemonset:
  enabled: true
config:
  sources:
    kubernetes:
      enabled: true
      prefix: "kubernetes#"
      keyDelimiter: "#"
  rewrites:
    set:
      time: "${kubernetes#time}"
  destinations:
    network:
    - transport: tcp
      address: logging-syslog-ng.logging.svc.cluster.local
      port: 601
      template: "$(format-json --key-delimiter # --scope all-nv-pairs)\\n"
      extraOptionsRaw: "time-reopen(10)"