SAST IDE benchmark: OIDC/GCP bootstrap needs refinement

OIDC module has been used in sast-ide-benchmark and sast-ide-integration in SAST IDE benchmark: use OIDC for GCP authentica... (#473433 - closed) • Hua Yan • 17.3.

However, there are still some improvements to be made:

• Documentation should be revised to be more easily understood.
  • If a process is described, number the steps
  • Clarify which GCP account and project must be established and provide gcloud command lines
  • if GCP console and gcloud can accomplish the same things, prefer gcloud
• The terraform scripts should be refined to remove redundancy like google-beta.
• Allocate automatically the service account in the way illustrated by OIDC module's sample script