Implementing accessibility non-regression check tool

[Samuel Thibault]

Hello Caolán,

It seems there is an unwanted effect: for instance 8d526da34810 ("weld
ScChiSquareTestDialog") turns input-range-button and output-range-button
from a foruilo-RefButton to a GtkButton, and a gla11y warning shows up.

In solenv/gbuild, gla11y is told that no labelling warning
should be emitted for foruilo-RefButton widgets because they are
auto-labelled Shrink/Expand, but the welding effort makes these
widgets normal GtkButton, and there is now no way for gla11y
to know that they are auto-labelled, thus the appearance of a
warning.

We could add some marking or put a label overwritten by the
auto-labelling in the .ui, but as discussed before we could as well just
put the suppression rules in solenv/sanitizers/ui/modules/scalc.false
to tell that there is nothing to fix here.

Samuel