Allowing to disable font rendering integration, making it possible to
build Mutter without pango/harfbuzz/fribidi dependencies.
This commit also adds a new clutter-pango header that is used to include
pango specific bits.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4106>
This is a step in cleaning up the Clutter context management. By making
it a GObject it's easier to add e.g. properties and features that helps
with introspection.
For now, this means the context creation is changed to go via a
"constructor" (clutter_create_context()). This is so that the global
context singleton can be mantained outsid of ClutterContext, until it
can be removed.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2016>
