[SDKMigration] Update Gallery.CredentialExpiration to use ManagedIdentity

[ryuyu]

Update Gallery.CredentialExpiration job to use Managed Identity for storage access.
This changeset also includes changes to add a new setting for local development.

Adding "Local_Development": boolean to the top level of app.json will now inject the relevant TokenCredential for use (DefaultAzureCredential for local development true, and ManagedIdentityCredential for local development false).

[drewgillies]

Discussed offline--the only potential for breakage here is the DI insertion for TokenCredential, which would conflict with any preexisting ones. It's unlikely such cases exist, but if they're found we could key them individually. Ideally, we would have the same approach applied to key vault access, which we could circle back to. If there are no concerns from the team and we move this approach forward, we can track that as separate work.