feat(ocm): Add update information to the /status API endpoint

[SamoKopecky]

Serve as the backend for operate-first/service-catalog#179

Add additional API call to gather information about cluster updates and provide it in the /status API endpoint. Also create tests for newly created functions.

I couldn't find an endpoint that only provides a single cluster, so I have to use the endpoint (internal.open-cluster-management.io/v1beta1/managedclusterinfos) even in the /status/:clusterName API endpoint.

Example of the new API response on /status/smaug (see the update section at the end):

{
  "name": "smaug",
  "status": {
    "available": true,
    "reason": "Managed cluster is available"
  },
  "consoleUrl": "https://console-openshift-console.apps.smaug.na.operate-first.cloud",
  "kubernetesVersion": "v1.22.3+fdba464",
  "oauthUrl": "https://oauth-openshift.apps.smaug.na.operate-first.cloud/oauth/token/implicit",
  "openshiftId": "5d448ae7-05f1-42cc-aacc-3122a8ad0184",
  "openshiftVersion": "4.9.21",
  "platform": "BareMetal",
  "allocatableResources": {
    "cpuCores": 1136.5,
    "memorySize": "7469511796Ki",
    "numberOfPods": 7750
  },
  "availableResources": {
    "cpuCores": 1152,
    "memorySize": "7505192052Ki",
    "numberOfPods": 7750
  },
  "update": {
    "available": true,
    "version": "4.9.53",
    "url": "https://access.redhat.com/errata/RHBA-2022:8714"
  }
}

[SamoKopecky]

/cc @tumido

[SamoKopecky]

Thanks for the feedback, changes pushed with a new commit.

[tumido]

/lgtm
/approve