Add extensions overload for Azure clients to use Arcus secret store

[stijnmoreels]

Is your feature request related to a problem? Please describe.
Currently, one has to pass in the connection string directly or via an IConfiguration instance if one wants to register an Azure EventHubs client to the application.

Describe the solution you'd like
Add an extension overload that lets you pass in a secret name which will be used when contacting the secret store.