add AutoRefreshingTokenCredential support to StorageAccountClient

[yvespp]

For vectordotdev/vector#8667 a way to refresh the managed identity token is needed. Vector is a log agent that can forward logs to azure blob storage. See also #739.

I add a way to pass TokenCredential to the StorageAccountClient so AutoRefreshingTokenCredential can be passed to it and the client can refresh the token automatically. I tested it locally using the added example.

I don't what's preferred here and can easily drop the second commit:

• In the first commit I used arc for TokenCredential and implemented Debug, PartialEq and Eq manually.
• In the second commit I just used box for TokenCredential and removed currently unused traits Clone, PartialEq and Eq.

[ghost]

All CLA requirements met.

[bmc-msft]

LGTM.

Thanks for the contribution!

With this adding support for the azure-identity crate, we can probably remove the bearer token methods, as azure-identity is a significantly better mechanism for managing bearer tokens.