Added the new function :c:func:`PyType_FromMetaclass`, which generalizes the
existing :c:func:`PyType_FromModuleAndSpec` using an additional metaclass
argument. This is useful for language binding tools, where it can be used to
intercept type-related operations like subclassing or static attribute access
by specifying a metaclass with custom slots.

Importantly, :c:func:`PyType_FromMetaclass` is available in the Limited API,
which provides a path towards migrating more binding tools onto the Stable ABI.
