Rename IAzureKeyVaultResource.GetSecretReference to GetSecret

[eerhardt]

Contributes to #7811

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
• Are you including unit tests for the changes and scenario tests if relevant?
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
• Does the change make any security assumptions or guarantees?
  • No
• Does the change require an update in our Aspire docs?
  • No

[Copilot]

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

src/Aspire.Hosting.Azure/IAzureKeyVaultResource.cs:33

• [nitpick] Consider updating the XML documentation for this method to reflect the new name 'GetSecret' for consistency.

IAzureKeyVaultSecretReference GetSecret(string secretName);

[eerhardt]

/backport to release/9.2

[github-actions]

Started backporting to release/9.2: https://github.com/dotnet/aspire/actions/runs/14317780207