Revert "label: Never measure more than max-width-chars"

Revert "label: Never measure more than max-width-chars"

This reverts commit ba44e7a228534ff066694ad97d25eaa23ec5f3af.

The change was meant to revert to old GTK3 behavior but it actually
broke new GTK4 behavior that is in use where max-width-chars is used to
determine an ideal size, but where we don't want to limit the width to
that size.

So what happens is the reintroduction of GTK3-style lots of whitepsace
bugs, and we really don't want those.

We also don't want to break backwards compat if we can avoid it.

So let's revert this.

The reftest that was made for this purpose has been adapted.

Fixes #4399