specs, test case for multiple clients and multiple groups

[weidongxu-microsoft]

source of real service https://github.com/Azure/azure-rest-api-specs/pull/29178

Cadl Ranch Contribution Checklist:

• [x] I have written a scenario spec
• [x] I have meaningful @scenario names. Someone can look at the list of scenarios and understand what I'm covering.
• [x] I have written a mock API
• [x] I have used @scenarioDocs for extra scenario description and to tell people how to pass my mock api check.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: fa63aed0b9fc99a1aeab297c58101ae3cff019ec

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ----------------------------- | ----- | | @azure-tools/cadl-ranch-specs | Patch |

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