[Telemtry] Move url lists of alexa1-10000 page to a json file.

Existing implementation of alexa1-10000 embeds the huge url list in
the python file, which is a terrible. It makes it super hard to navigate
through the file, or review its content, and make it harder to update the
alexa1-10000 pages if needed.

Review URL: https://codereview.chromium.org/915303002

Cr-Commit-Position: refs/heads/master@{#316012}
3 files changed