Defer YARP resource endpoint resolution

[danegsta]

Description

Defer YARP cluster target resolution for resource, endpoint, and external service destinations until environment configuration is generated. This ensures resource endpoint scheme changes made late in AppHost startup, such as AddUvicornApp automatically upgrading its primary endpoint to HTTPS when a developer certificate is available, are reflected in YARP's generated reverse proxy destinations.

Resource targets now resolve through endpoint-aware logic consistent with explicit endpoint targets: scheme-named endpoints resolve as scheme://resource, while named endpoints resolve with the DNS-SD named endpoint form such as http://_api.resource.

Added regression coverage for late endpoint scheme updates and named endpoint resource resolution.

Fixes #16831

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.dev issue:
      • New issue
  • No

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/microsoft/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 16834

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/microsoft/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 16834"