As with the previous two commits, the results of calling
`gi_repository_get_loaded_namespaces()` were previously
non-deterministic due to being generated by iterating over a hash table,
which has a non-deterministic iteration order.

Fix that by using the new `ordered_typelibs` and `ordered_lazy_typelibs`
arrays to provide deterministic ordering.

At the same time, significantly reduce the number of allocations needed
to build the return value — previously the results would be built as a
linked list before being turned into an array. The linked list is now
banished to history.

Add some more unit tests to maximise test coverage of this method.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Fixes: #3303