Add compiler explorer option to hide collapsed stages

[anderseknert]

We often use screenshots from the compiler explorer to demonstrate how something is rewritten by the OPA compiler. This is sometimes made more difficult by the fact the stages of interest won't fit on a single screen when the explorer lists all the stages in between — including those that made no difference for the result. As an example:

package p

allow if not "a" in input.foo.bar

Displays as:

With the relevant output found just further down:

This isn't a huge issue, but I think it would be great if there was a toggle to completely hide all stages without any output, to better visualize the stages where the action is.