This commit introduces our own Azure storage provider by wrapping Kopia's implementation rather than contributing to upstream based on the following considerations:
1. Velero needs the capability to interact with the repository concurrently while Kopia doesn't, this will increase the complexity of Kopia if we contribute to upstream
2. The configuration items provided by Velero and Kopia are conflict, e.g. Velero supports customizing storage account URI which is a full path while Kopia supports customizing storage account domain which is part of the URI. We need to consider the backward compatibility and upgrade case if we contribute to upstream which needs extra efforts
3. Contribute to upstream is a longer cycle when we need to introduce new changes. With this commit, we no longer depends on upstream for the Azure storage provider part and is easy for us to maintain
Signed-off-by: Wenkai Yin(尹文开) <yinw@vmware.com>
