This implements the OpenChunkWriter interface for azureblob which
enables multi-thread uploads.
This makes the memory controls of the s3 backend inoperative; they are
replaced with the global ones.
--azureblob-memory-pool-flush-time
--azureblob-memory-pool-use-mmap
By using the buffered reader this fixes excessive memory use when
uploading large files as it will share memory pages between all
readers.
This commit switches from using the old Azure go modules
github.com/Azure/azure-pipeline-go/pipeline
github.com/Azure/azure-storage-blob-go/azblob
github.com/Azure/go-autorest/autorest/adal
To the new SDK
github.com/Azure/azure-sdk-for-go/
This stops rclone using deprecated code and enables the full range of
authentication with Azure.
See #6132 and #5284