Add configuration agent health event for Postgres

[sethsamuel]

What does this PR do?

• Migrates Postgres config to the InstanceConfg model
• Adds and extends config validation
• Emits an agent health event when a config is loaded

Motivation

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

❌ Patch coverage is 90.97104% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.25%. Comparing base (f72a071) to head (263d8d5).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

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[eric-weaver]

Why hidden?

[sethsamuel]

This is to match current spec. For some reason all the properties were hidden but not the top level