Use as short version numbers as is relevant for each browser

[foolip]

In the browser picker, we use the full version numbers, which isn't very important to show, and means that we get longer lists where it's harder to find what you're looking for, especially if you're looking for a specific version and platform.

Should probably be consistent with https://github.com/w3c/wptdashboard/issues/494 (and https://github.com/w3c/wptdashboard/issues/493).

[foolip]

Screenshot of the problem:

[foolip]

I'd like to use https://github.com/mdn/browser-compat-data/tree/master/browsers to get the release dates, and then we could also use the BCD versions as canonical.