Add an endpoint to KOTS where application metrics can be retrieved adhoc

[sgalsaleh]

What this PR does / why we need it:

Adds an endpoint to KOTS where application metrics can be retrieved adhoc to facilitate the KOTS/SDK integration and telemetry reconciliation.

Which issue(s) this PR fixes:

Fixes SC-88179

Special notes for your reviewer:

Example responses:

• Valid license ID:

$ curl -s -H 'Authorization: <valid-license-id>' 10.43.247.154:3000/api/v1/app/metrics | jq .
{
  "X-Replicated-AppStatus": "ready",
  "X-Replicated-ClusterID": "qqtiozrovtsrtgibwfwvydghauchpmhw",
  "X-Replicated-DownstreamChannelID": "2TiLbGfE9YRXAPM2JCD9STfS11B",
  "X-Replicated-DownstreamChannelSequence": "18",
  "X-Replicated-DownstreamSequence": "1",
  "X-Replicated-DownstreamSource": "Upstream Update",
  "X-Replicated-GitOpsProvider": "",
  "X-Replicated-InstallStatus": "failed",
  "X-Replicated-InstanceID": "2W2EEjXOPlO7kdWRVtX7FetgCMp",
  "X-Replicated-IsGitOpsEnabled": "false",
  "X-Replicated-IsKurl": "true",
  "X-Replicated-K8sDistribution": "k3s",
  "X-Replicated-K8sVersion": "v1.20.2+k3s1",
  "X-Replicated-KotsInstallID": "dev-1pu4oeY162e2pbLpK4JubK6hxrX",
  "X-Replicated-KurlNodeCountReady": "1",
  "X-Replicated-KurlNodeCountTotal": "1",
  "X-Replicated-NativeHelmInstalls": "0",
  "X-Replicated-ReplHelmInstalls": "0",
  "X-Replicated-SkipPreflights": "true"
}

• Invalid license ID:

$ curl -s -H 'Authorization: invalid-license-id' 10.43.247.154:3000/api/v1/app/metrics | jq .
{
  "error": "license ID is not valid",
  "success": false
}

• No authorization header / license ID:

$ curl -s 10.43.247.154:3000/api/v1/app/metrics | jq .
{
  "error": "missing authorization header",
  "success": false
}

Steps to reproduce

Does this PR introduce a user-facing change?

NONE

Does this PR require documentation?

NONE