Backport of Audit: log 'warnings' from eventlogger even if audit is deemed a success into release/1.17.x

[hc-github-team-secure-vault-core]

Backport

This PR is auto-generated from #27809 to be assessed for backporting due to the inclusion of the label backport/1.17.x.

The below text is copied from the body of the original PR.

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Description

Within audit there exists an scenario where the eventlogger broker reports that audit was deemed a success (because it managed to successfully log to at least 1 sink node), but there were warnings (errors) that came back from other audit devices where audit failed.

We want to ensure that we capture these warnings in the server log so that they don't go missing because we managed to log to a single device.

This PR has ENT and CE components.

HashiCorp Checklist

• Labels: If this PR is the CE portion of an ENT change, and that ENT change is
  getting backported to N-2, use the new style backport/ent/x.x.x+ent labels
  instead of the old style backport/x.x.x labels.
• Labels: If this PR is a CE only change, it can only be backported to N, so use
  the normal backport/x.x.x label (there should be only 1).
• 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.
• 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.
• ENT PR: If this change has an associated ENT PR, please link it in the
  description. Also, make sure the changelog is in this PR, not in your ENT PR.

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Overview of commits

• 39b99b2

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