While at it, use a single variable for glib, gio and gobject

Removes several of the following:
 > ../tests/test-gom-transform.c:170:3: warning: ‘g_type_class_add_private’ is deprecated [-Wdeprecated-declarations]
 >   170 |   g_type_class_add_private(object_class, sizeof(ItemResourcePrivate));
 >       |   ^~~~~~~~~~~~~~~~~~~~~~~~

The G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE call was moved as it needs to
know the storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

The G_DEFINE_TYPE_WITH_PRIVATE call was moved as it needs to know the
storage size of private structure.

It was missing context, and a way to verify correctness, so disable it
until something better is needed.

It needs a terminating value for the va_list.

Now that we are notifying the API consumer of the error, let them crash
instead of Gom for the missing resource.

If fetch was active while a get_index() was called, the GHashTable could
be mutated while a reader exists.

This fixes that by protecting it with a mutex and then inserting all of
the items from the worker in one go.

Such use is what you might expect if you're paginating data and lazy
loading regions of the resource group.

Recent changes will be part of the new release, not 0.4. Bump now so
that projects can require them at build time.