MXH update to solovev has brought in some runtime dispatching

[orso82]

@lstagner there is likely some type instability going on here:

The issue can be replicated with the following:

@profview MXHEquilibrium.solovev(4.713171689711136, MXHEquilibrium.MillerExtendedHarmonicShape{4, Float64}(4.824427963855637, 0.0, 0.2857127805570335, 2.316652874254983, 0.006108356192724909, [-0.005785496776103992, 0.0019621533056812094, 0.0008731423301050459, -0.0023067252622236507], [0.6779183625351539, -0.024448107498341847, -0.07279476450802957, -0.062044503693775954]),-1.6736002249794346, 2.567112148732714;diverted=true)