We were looking at the wrong class names here, we need
to look at the owner type to match against our list.
This fixes problems where gtk-builder-tool simplify
inadvertedly loses hexpand or vexpand settings, messing
up layout, as recently happend in gtk4-widget-factory.
Rewrite the builder-tool simplify command to have
a full parse tree around, and perform simplifications
on that tree. This lets us rewrite GtkStack and turn
child properties into child meta objects.
We wrap SVG data from icons within another SVG with extra styling
information. The wrapped SVG may contain characters that cannot be
part of a data: URL (https://fetch.spec.whatwg.org/#data-urls).
Librsvg 2.45 got more strict in its parsing of data: URLs; whereas
previously it ignored '#' characters in them, now it considers them to
be the start of a fragment identifier, which is not allowed in data:
URLs anyway.
To avoid unallowed characters, we now create a data: URL with a
base-64 encoded SVG.
Fixes https://gitlab.gnome.org/GNOME/gtk/issues/1471
