feat: Azure identity for azure storage auth

[johanandren]

Ammend the azure-storage auth options with azure-identity, enabling OAuth2 bearer token authentication.

• Opt in dependency on azure-identity to not bring in the entire dependency graph by default, users opt in with an explicit dependency to actually use it
• When authorization-type is set to BearerToken in config, DefaultAzureCredential is used automatically, supporting managed identity, workload identity, environment credentials, etc.
• Users can also provide any custom TokenCredential programmatically via StorageSettings.withTokenCredential(credential), e.g. for User Assigned Managed Identity
  with a specific client ID
• Token acquisition is async (bridges the Azure SDK Mono into the Akka Stream via Source.future), token caching/refresh handled by the Azure SDK internally

[octonato]

Solid PR. Certified by deep expert.

I left two minor suggestions, but worth doing before merging.

[johanandren]

I'm trying to add an integration test against azurite as well, before merging this.