Ability to fetch a GCS file given a URL

[sambostock]

Is your feature request related to a problem? Please describe.
Given a gs://bucket/path?generation=... URL, it would be nice to be able to fetch a file without needing to manually split the URL into pieces.

Describe the solution you'd like
A method could exist to do the splitting automatically and fetch the specified file. For example:

• Google::Cloud::Storage#file_from_url
• Google::Cloud::Storage::File.from_url

Describe alternatives you've considered
The current approach involves manually extracting the pieces of the URL to construct

bucket, path, options = split_url_please(gs_url)
Google::Cloud::Storage.new(project_id: '...').bucket(bucket).file(path, **options)