Adapt gardener adminkubeconfig in local_setup script

[unmarshall]

What this PR does / why we need it:
Changes local_setup.sh script which has now been refactored and introduces the following enhancements:

• New Usage:

      Usage: local_setup.sh [Options]
      Options:
        -d | --seed                       <seed-cluster-name>                 (Required) Name of the Gardener Seed Cluster
        -t | --shoot                      <shoot-cluster-name>                (Required) Name of the Gardener Shoot Cluster
        -p | --project                    <project-name>                      (Required) Name of the Gardener Project
        -i | --provider                   <provider-name>                     (Required) Infrastructure provider name. Supported providers (gcp|aws|azure|vsphere|openstack|alicloud|metal|equinix-metal)
        -l | --landscape                  <landscape-name>                    (Optional) Name of the landscape. Defaults to dev
        -k | --kubeconfig-path           <absolute-kubeconfig-path>           (Optional) Target path to store the control and target KubeConfigs. Default: <PROJECT-DIR>/dev/kube-configs
        -m | --mcm-provider-project-path <absolute-mcm-provider-project-dir>  (Optional) MCM Provider project directory. If not provided then it assumes that both mcm and mcm-provider projects are under the same parent directory
        -e | --kubeconfig-expiry-seconds <expiry-duration-in-seconds>         (Optional) Common expiry durations in seconds for control and target KubeConfigs. Default: 3600 seconds

• Generates short-lived admin kubeconfigs.
• Introduced another script local_restore.sh which scales back MCM deployment to 1 and also removes the annotation that prevents DWD to scale MCM down.

     Usage: local_restore.sh [Options]
    Options:
      -t | --shoot                      <shoot-cluster-name>                (Required) Name of the Gardener Shoot Cluster
      -p | --project                    <project-name>                      (Required) Name of the Gardener Project
      -l | --landscape                  <landscape-name>                    (Optional) Name of the landscape. Defaults to dev
      -i | --provider                   <provider-name>                     (Required) Infrastructure provider name. Supported providers (gcp|aws|azure|vsphere|openstack|alicloud|metal|equinix-metal)
      -k | --kubeconfig-path            <relative-kubeconfig-path>          (Optional) Relative path to the <PROJECT-DIR> where kubeconfigs will be downloaded. Path should not start with '/'. Default: <PROJECT-DIR>/dev/kube-configs
      -m | --mcm-provider-project-path  <absolute-mcm-provider-project-dir> (Optional) MCM Provider project directory. If not provided then it assumes that both mcm and mcm-provider projects are under the same parent directory

• Added a new target in Makefile to add license headers. Quite a lot of files are missing them.

Which issue(s) this PR fixes:
Fixes #844

Special notes for your reviewer:

Release note:

A new make target is introduced to add license headers.

[himanshu-kun]

Thanks for the changes and additions, script usage looks much better now (will try it as well)

Didn't know we had so many files without licenses XD (or does it update the licenses also?)
will give lgtm after trying once (reviewer responsibility :p)

[unmarshall]

As discussed @himanshu-kun will create a separate issue to update all providers with the following changes:

1. Add an empty .env file (copy it from mcm)
2. Adapt Makefile (include .env and remove the statically defined variables)

[himanshu-kun]

/lgtm

[himanshu-kun]

Updated the changes made here in #852