Removed introspectiontools.class_to_tools_package_qualified_class_name()
from public API.

The functionality was used only by AbjadObject.

The functionality is now implemented as a private method bound to AbjadObject.

The introspectiontools package is now deprecated. A coming commit will move
introspectiontools.get_current_function_name() to testtools. The
instrospectiontools package will then be empty.