CDN domain should be returned by the TVM

Currently the CDN url for prod/stage is hardcoded in files lib, a better approach would be to return it from the TVM, just like the TVM also returns the blob storage account.

Start by locating the hardcoded production and staging CDN URLs in the lib files and the existing TVM lookup that returns the blob storage account. Trace how that value reaches the file-system API and identify any related tests. Done means the CDN URL for each environment comes from the TVM rather than a hardcoded value.

Written by the indexing model from the issue text.