Optionally add `azcopy` to the `azure-cli` feature

`azcopy` is a very useful tool for copying large amounts of data to/from Azure Storage.

How to install:

```bash
curl -Lo azcopy.tar.gz https://aka.ms/downloadazcopy-v10-linux && \
tar -xf azcopy.tar.gz && \
mv azcopy_linux_amd64_*/azcopy /usr/local/bin/azcopy && \
rm -rf azcopy_linux_amd64_* && \
chmod +x /usr/local/bin/azcopy
```