feat(upgrade): add support for UpgradeTask CR

[shubham14bajpai]

This PR adds support for upgrades via UpgradeTask CRs. This enables users to create UpgradeTask CRs for the resources to be upgraded and group them using labels. Then a job can be launched with the env UPGRADE_TASK_LABEL which will list and upgrade the resources sequentially. For more details refer: https://github.com/openebs/openebs/blob/master/contribute/design/1.x/upgrade/volume-pools-upgrade.md

This PR also fixes the issue: openebs/openebs#3069
Now the upgrade job does not defaults to quay.io/openebs as the prefix but will take whatever the prefix was on the previous version as default.

Sample test result:

• for pools each cspi similar upgradetask CR will be generated.

apiVersion: openebs.io/v1alpha1
kind: UpgradeTask
metadata:
  creationTimestamp: "2020-06-26T09:39:16Z"
  labels:
    resource: cstorPool-xqd89
  generation: 6
  name: upgrade-cstor-cspi-cspc-stripe-wx49
  namespace: openebs
  resourceVersion: "5395"
  selfLink: /apis/openebs.io/v1alpha1/namespaces/openebs/upgradetasks/upgrade-cstor-cspi-cspc-stripe-wx49
  uid: 85a934a6-97f6-43fc-9355-73ff69d08315
spec:
  cstorPoolInstance:
    cspiName: cspc-stripe-wx49
  fromVersion: 1.10.0
  imagePrefix: ""
  imageTag: 1.11.0
  toVersion: 1.11.0
status:
  completedTime: "2020-06-26T09:40:27Z"
  phase: Success
  retries: 0
  startTime: "2020-06-26T09:39:16Z"
  upgradeDetailedStatuses:
  - lastUpdatedAt: "2020-06-26T09:39:16Z"
    message: Pre-upgrade steps were successful
    phase: Completed
    startTime: "2020-06-26T09:39:16Z"
    step: PRE_UPGRADE
  - lastUpdatedAt: "2020-06-26T09:40:27Z"
    message: Pool upgarde was successful
    phase: Completed
    startTime: "2020-06-26T09:39:16Z"
    step: POOL_INSTANCE_UPGRADE

• for volumes similar upgradetask CR will be generated.

apiVersion: openebs.io/v1alpha1
kind: UpgradeTask
metadata:
  creationTimestamp: "2020-06-26T09:43:30Z"
  generation: 9
  labels:
    resource: cstorVolume-z5Qdh
  name: upgrade-cstor-csi-volume-pvc-ce7fc00f-3476-4a4a-950a-bc45aa52e5ce
  namespace: openebs
  resourceVersion: "6056"
  selfLink: /apis/openebs.io/v1alpha1/namespaces/openebs/upgradetasks/upgrade-cstor-csi-volume-pvc-ce7fc00f-3476-4a4a-950a-bc45aa52e5ce
  uid: 60895e97-3086-422f-8567-d7f348765561
spec:
  cstorVolume:
    pvName: pvc-ce7fc00f-3476-4a4a-950a-bc45aa52e5ce
  fromVersion: 1.10.0
  imagePrefix: ""
  imageTag: ""
  toVersion: 1.11.0
status:
  completedTime: "2020-06-26T09:45:14Z"
  phase: Success
  retries: 0
  startTime: "2020-06-26T09:43:38Z"
  upgradeDetailedStatuses:
  - lastUpdatedAt: "2020-06-26T09:43:38Z"
    message: Pre-upgrade steps were successful
    phase: Completed
    startTime: "2020-06-26T09:43:38Z"
    step: PRE_UPGRADE
  - lastUpdatedAt: "2020-06-26T09:43:49Z"
    message: Replica upgrade was successful
    phase: Completed
    startTime: "2020-06-26T09:43:38Z"
    step: REPLICA_UPGRADE
  - lastUpdatedAt: "2020-06-26T09:45:14Z"
    message: Target upgrade was successful
    phase: Completed
    startTime: "2020-06-26T09:43:49Z"
    step: TARGET_UPGRADE

[kmova]

Looks good to me. We can merge after @sagarkrsd is ok with this as well.

[kmova]

@shubham14bajpai - could you also update this PR with any tests that were performed.

[sagarkrsd]

Looks good to me. Some minor comments only.