Integration: Switch to using auth Gcloud action in Windows workflow.

Following the forking of `github-google-actions/setup-gcloud` into
individual actions, the functionality for authenticating on Google
Cloud within GitHub workflows has been moved to the
`github-google-actions/auth` action.

This patch updates the Windows Periodic Integration test workflow to use
the new `auth` action, as well as switching to using Workload Identity
Federation-based authorization which is superseding the Service Account
Key-based authorization the Windows Periodic workflow was using thus far.

Signed-off-by: Nashwan Azhari <nazhari@cloudbasesolutions.com>

.github/workflows/windows-periodic-trigger.yml

@@ -21,5 +21,5 @@ jobs:
     secrets:
       AZURE_SUB_ID: "${{ secrets.AZURE_SUB_ID }}"
       AZURE_CREDS: "${{ secrets.AZURE_CREDS }}"
-      GCP_PROJECT_ID: "${{ secrets.GCP_PROJECT_ID }}"
-      GCP_SA_KEY: "${{ secrets.GCP_SA_KEY }}"
+      GCP_SERVICE_ACCOUNT: "${{ secrets.GCP_SERVICE_ACCOUNT }}"
+      GCP_WORKLOAD_IDENTITY_PROVIDER: "${{ secrets.GCP_WORKLOAD_IDENTITY_PROVIDER }}"