SE 5.3.0 beta 4: Navigating between Settings categories within one Settings session

I mentioned this in #12087 but it's probably lost. So let's make it stand out.

This is inspired by the way Firefox works. If you look at a number of categories in one invocation of Settings, let the user navigate back & forth along that string of categories using Alt+Left/RightArrow, same as in Firefox. The categories don't necessarily have to be adjacent in the column of category buttons. It applies only during one invocation of Settings, This history should be forgotten when you close Settings.