Use options specific factory to create `BlobContainerClient`

[ronaldbarendse]

This fixes https://github.com/umbraco/Umbraco.StorageProviders/issues/43 by allowing users to customize the way the BlobContainerClient is created from the AzureBlobFileSystemOptions using:

• AddAzureBlobMediaFileSystem(options => options.CreateBlobContainerClientUsingDefault()) - this is overly verbose to add by default, but allows users to reset any customizations back to the default factory (that uses the ConnectionString and ContainerName);
• AddAzureBlobMediaFileSystem(options => options.CreateBlobContainerClientUsingOptions(_blobClientOptions)) - this is similar to the default factory, but uses custom a BlobClientOptions (allowing you to e.g. configure retry policies);
• AddAzureBlobMediaFileSystem(options => options.TryCreateBlobContainerClientUsingUri(uri => new BlobContainerClient(uri, _blobClientOptions))) - if the ConnectionString can be parsed into a valid URI, this factory will be used, otherwise it will fall back to the previous set/default one.

The TryCreateBlobContainerClientUsingUri() can be used to provide a DefaultAzureCredential instance (after adding the Azure.Identity package) to enable access using managed identities.

[JvaNovicell]

@ronaldbarendse Any chance this will get merged anytime soon?