Consider adding exempt delegation dual governance

[hxrts]

Since validators must have a certain amount of exempt stake we have some expectation that these tokens will not be rehypothecated (still possible, but we've made it more challenging and highly stigmatized).

We could therefore give this exempt stake very limited backstop power to pause messages originating from accounts holding delegation shares. This backstop would be enacted via special expedited governance proposal available only to exempt stake.