UI/String freeze break request for gnome-boxes

[Felipe Borges <felipeborges gnome org>]

Hi,

Since the release of GNOME Boxes 3.32.0 this week, we started to get
reports from users having problems with our recent "auto enable 3D
acceleration" feature. For this small set of users (dual-GPU or
unconventional graphics drivers), Boxes has become unusable.

That's why I have proposed the following merge request
https://gitlab.gnome.org/GNOME/gnome-boxes/merge_requests/133

These changes introduce a pop-up notification that shows up only at
the first time a user starts a machine that supports 3D acceleration.
The notification offers an user action to Disable 3D acceleration.
Other than UI, it introduces two new strings:
"Experiencing graphics problems?" and "Disable 3d acceleration".

Screenshot -> https://i.imgur.com/EYC5IDa.jpg
(by the way, those glitches you see in the screenshot are the ones
worked-around by this).

I have discussed the approach with both Jakub Steiner and Allan Day,
and their are onboard with the change.

Thanks, and sorry for the inconvenience of making this request this
late in the release cycle.

Felipe.