Create symlink via azure.storage.file FileService

### Which service(blob, file, queue) does this issue concern?
Note: for package version >= 12.0.0 please post the issue here instead: https://github.com/Azure/azure-sdk-for-python/issues
for table service, please post the issue here instead: https://github.com/Azure/azure-cosmosdb-python.
azure.storage.file

### Which version of the SDK was used? Please provide the output of `pip freeze`.
azure-storage-file==2.1.0

### What problem was encountered?
I'm trying to figure out how to create a symlink via the azure-storage-file FileService interface. Ideally, the symlink target doesn't need to exist, but I can work around that if need be. To be clear, I want the symlink uploaded, not the content of the symlink'ed file.

I should also clarify I am talking about a soft symlink here.

### Have you found a mitigation/solution?
No, I haven't been able to find a good example of how to accomplish this.

Start with the azure.storage.file FileService interface and the azure-storage-file 2.1.0 API documentation, focusing on how file uploads represent symbolic links. Determine whether soft-link objects are supported independently of their targets and what API behavior would define completion; the issue names no source files or tests.

索引モデルが issue の本文から書いたものです。