[WIP] Add mermaid diagram for unifying current clients

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

help create a mermaid diagram for the following: Unify Current Clients with variable install i.e pip install azure-mgmt-unified[keyvault] and getting just keyvault basics. Fundamentally the emitter for this method would not need to be that different than our current emitter. We would have a single entry point for all of the mgmt packages.

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