Add health checks to eventhubs emulator.

[mitchdenny]

Description

This PR adds a health check to the EventHubs emulator so it works with WaitFor.

Related #5645

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
• 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

[davidfowl]

cc @oising

[davidfowl]

/azp run

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