Getters for Vm and Va in ExaAdmm backend

[michel2323]

Currently, Va and Vm are set to zero.

ProxAL.jl/src/ExaAdmmBackend/interface.jl

Lines 54 to 61 in ba5af18

	function voltage_magnitude(model::ModelProxAL, sol::ExaAdmm.Solution)
	nbus = model.grid_data.nbus
	return zeros(nbus)
	end
	function voltage_angle(model::ModelProxAL, sol::ExaAdmm.Solution)
	nbus = model.grid_data.nbus
	return zeros(nbus)
	end