[storage] az storage file copy start-batch --snapshot feature

**Is your feature request related to a problem? Please describe.**

az storage file copy start-batch does not support snapshot restore

**Describe the solution you'd like**
Describe the solution you'd like
Wanted to check if we could add `--file-snapshot`and/or `--snapshot` support for` az storage file copy start-batch`? Right now file snapshot is only supported on az storage file copy start

By adding the snapshot, we can restore all files from our file share snapshot to the _same_ file share or a _different_ file share.

**Describe alternatives you've considered**

**Additional context**

Thanks!