* azure: support external dependencies and outputs
- Implement get_file_checksum with get_etag
- Implement a DependencyAzure and OutputAzure classes
- Add AzureOutput to OUTS, OUTS_MAP and CHECKSUMS_SCHEMA
- Add AzureDependency to DEPS and DEPS_MAP
- Add unit tests for AzureOutput and AzureDependency
Fixes#3540.
* Use content_md5 instead of etag
The etag is different for the same file in different locations.
* Use etag and remove external outputs for Azure
Due to inconsistencies with Azure's Content-MD5 property, it is not
stable enough to be used at the moment. Using the etag offers enough
reliability to support external dependencies. See also:
https://discordapp.com/channels/485586884165107732/565699007037571084/713462619469643796
