ACA Container volumes use shared access keys

When using container volumes in an ACA app, we are generating an Azure Storage account for storing those volumes.

However, the way the access from ACA to this storage account happens is via access keys:

https://github.com/dotnet/aspire/blob/8fd92afd7f3d9168c96f52f147a7b301b78ad349/src/Aspire.Hosting.Azure.AppContainers/AzureContainerAppExtensions.cs#L202-L215

This means that an Azure Storage account is created that allows shared key access, which may trigger security rules in environments that don't want to allow Azure Storage accounts with access keys.

We should be using managed identities here instead, to allow communication between the ACA container and the Storage account.