Update the BigBang HelmRelease with optional `verify` block

For the BigBang Chart when deploying with flux, we would need to add the HelmRelease updated with conditional verify block.

verify:
  provider: cosign
  secretRef:
    name: cosign-pub

An OCI HelmRepository will also be needed.

Acceptance Criteria:

• BigBang Chart is installed using OCI Helm Artifact
• BigBang Chart is verified using flux