add support to restore in a cluster with different nodes

[pawanpraka1]

Right now there is a limitation where we can restore in a cluster which should have same nodes (names only) present. We can add a config map where node mappings are given and while restore time we can use this to map the nodes.

apiVersion: v1
kind: ConfigMap
metadata:
  # any name can be used; Velero uses the labels (below)
  # to identify it rather than the name
  name: change-pvc-node-selector-config
  # must be in the velero namespace
  namespace: velero
  # the below labels should be used verbatim in your
  # ConfigMap.
  labels:
    # this value-less label identifies the ConfigMap as
    # config for a plugin (i.e. the built-in restore item action plugin)
    velero.io/plugin-config: ""
    # this label identifies the name and kind of plugin
    # that this ConfigMap is for.
    velero.io/change-pvc-node: RestoreItemAction
data:
  # add 1+ key-value pairs here, where the key is the old
  # node name and the value is the new node name.
  <old-node-name>: <new-node-name>