Update Search results to be tabbed by the distro of interest

[tfoote]

We can reuse the layout of the package listings, Right now we get N copies of each package from the N distros it's available in. It would be much cleaner to filter the search by the distro of interest and show tabs across the top to select a different distro in the same way we do for the Package list.

An enhancement could be to show the count of responses in each tab to indicate that different tabs might have other responses.

If you search for tf2_ros you get a whole page of listings of the same package. https://index.ros.org/search/?term=tf2_ros&section=pkgs

[rkent]

As discussed in #415, I am proposing something similar but as a major rewrite of the table.