implement an R-cran lister

As discussed on IRC, at current the approach that is known is to use https://cran.r-project.org/web/packages/available_packages_by_name.html url to list all the packages, the response that is returned by this page is HTML code. Hence to make a lister that is more reliable, there is a need to find some other source to list all the packages.

Migrated from T1709 (view on Phabricator)

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