Converts to an underlying fs provider resource format. Returns undefined if the given resource is not valid resource.
For example converting user-storage resources to file resources under a user home:
user-storage:/user/settings.json => file://home/.theia/settings.json
user-storage:/settings.json => undefined
Converts from an underlying fs provider resource format.
For example converting
fileresources under a user home touser-storageresource: