Add addoption by annotation feature

[michaelhtm]

Issue #, if available:

Description of changes:
These changes introduce a new feature gate called ForceAdoptResources
which allows users to provide the read required fields in the annotation and
an empty spec, and the controller would populate the resource and adopt
from AWS

Here's an example for cluster:

apiVersion: eks.services.k8s.aws/v1alpha1
kind: Cluster
metadata:
  name: my-cluster
  annotations:
    services.k8s.aws/force-adoption: "true"
    services.k8s.aws/adoption-fields: | 
        {
          "name": "my-cluster"
        }

Here's another one to adopt a nodegroup

apiVersion: eks.services.k8s.aws/v1alpha1
kind: NodeGroup
metadata:
  name: my-ng
  annotations:
    services.k8s.aws/force-adoption: "true"
    services.k8s.aws/adoption-fields: | 
        {
          "name": "ng-12324",
          "clusterName": "my-cluster"
        }

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ack-prow]

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This pull-request has been approved by: michaelhtm
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[ack-prow]

@michaelhtm: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
verify-attribution	3fd1d42	link	false	/test verify-attribution
ecr-controller-test	3fd1d42	link	true	/test ecr-controller-test
iam-controller-test	3fd1d42	link	true	/test iam-controller-test
s3-controller-test	3fd1d42	link	true	/test s3-controller-test

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