Use tabular figures by default in Adwaita for all UI elements

The new Cantarell defaults to proportional figures for text use. This will cause numbers to jump when changing and not line up with figures above and below.

To solve this, enable the "tnum" OpenType feature by default for all UI elements, maybe even the lining figures "lnum" feature. This will work with all (non-broken) fonts that use non-lining, non-tabular numbers by default.

This should be solved before 3.28 is released with the new Cantarell.