Replace health check publisher and scheduler with ResourceHealthCheckService and introduce ResourceReadyEvent.

[mitchdenny]

Description

This PR removes the health check publisher and scheduler and combines it into a single ResourceHealthCheckService which runs in the background doing health checks on a per resource basis.

Fixes #5602
Fixes #5638
Fixes #5871
Fixes #5943

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No (existing tests provide coverage - internal mechanism now relies on this event)
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue:
  • No

Microsoft Reviewers: Open in CodeFlow

[mitchdenny]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mitchdenny]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mitchdenny]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[davidfowl]

Follow up: Make ResourceHealthCheckService more testable using the time provider and add more logs.