Audit: add auth and secret block to response test for hmac

[peteski22]

Description

Add test to prevent regression of HMAC for auth within a response for audit.

Related PR: #28236

TODO only if you're a HashiCorp employee

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  • 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.
• ENT Breakage: If this PR either 1) removes a public function OR 2) changes the signature
  of a public function, even if that change is in a CE file, double check that
  applying the patch for this PR to the ENT repo and running tests doesn't
  break any tests. Sometimes ENT only tests rely on public functions in CE
  files.
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[kubawi]

LGTM, thanks Pete!

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