Improve elicitation testing

[alzimmermsft]

PR #1501 ran into an issue where the mocking for elicitation testing was missing a required field as of the 2025-06-08 MCP spec (though the spec web page didn't include that information until the 2025-11-26 version).

We should review the elicitation portion of the spec and add in missing tests for URL elicitation and add in tests that explicitly set form elicitation in addition to the default handling which is form (just in case the default changes in the future or if explicitly setting elicitation type becomes required).

• Add URL elicitation tests
• Add explicit form elicitation tests

[anannya03]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @microsoft/azure-mcp.