Add scope_types attribute to the BaseCheck class

Neutron, based on the defined policy rules is creating check
objects "in flight" to e.g. include check some object's attributes,
like e.g. network's provider parameters.
That use case requires that BaseCheck class and classes which inherits
from it needs to have scope_types defined thus Neutron can set it for
the Check based on the defined policy rule.

This patch adds scope_types attribute to the BaseCheck class to make it
available for use cases like described above.

Related-Bug: #1923503
Change-Id: Ibf30d0ffa5e9b125742089705d3557c02a03bc43