Backport of improve autopilot logging when it starts up into release/1.17.x

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

Backport

This PR is auto-generated from #27464 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

While dealing with an autopilot escalation, I noticed that the logging when autopilot starts up is suboptimal, for a few reasons.

• The struct that is written to the logs is fairly useless, as you only see values, not struct member names
• If the autopilot reconcile interval hasn't been modified via the config (which is the case the overwhelming majority of the time, I imagine) then reconcile_interval 0s is printed to the logs, which is incorrect, and actually alarming. What's happening is it's printing out the value of the reconcile interval as it exists on the raft backend, which is 0 by default, but that's not actually the value autopilot is using. This is misleading.

This makes the autopilot config struct print in a better way and also updates the logging to not actually print the values for reconcile interval or update interval unless they were actually changed from their defaults.

TODO only if you're a HashiCorp employee

• 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

• f33f1b1

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