postgres backend storage: adding support for azure auth

[tauhid621]

Description

This PR upgrades the go-pgmultiauth module version which now supports workload identity based auth in Azure.

The new auth mode azure will handle both workload identity and managed identity. azure_msi has not been removed to ensure we do not break the existing flow.

TODO only if you're a HashiCorp employee

• Backport Labels: If this fix needs to be backported, use the appropriate backport/ label that matches the desired release branch.
  • LTS: If this fixes a critical security vulnerability or severity 1 bug, it will also need to be backported to the current LTS versions of Vault. To ensure this, use all available enterprise labels.
• Jira: If this change has an associated Jira, it's referenced either in the PR description, commit message, or branch name.
• RFC: If this change has an associated RFC, please link it in the description.

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.
• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've documented the impact of any changes to security controls.

Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.

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