Override AbstractSoilHydrologyClosure broadcast behavior

[imreddyTeja]

Purpose

Previously, the "Phase change source term" failed when run on a GPU.
Closes #860

The fix is adding
Base.broadcastable(BC::vanGenuchten) = Ref(BC)

I tried adding Base.broadcastable(BC::vanGenuchten) = tuple(BC) as suggested here, but that does not fix the error.

To-do

Content

• isolated the problem to broadcasting over vanGenuchten struct
• fixed by overriding the broadcast behavior for vanGenuchten struct
• also applied the fix to BrooksCorey struct, even though it is not causing any failures

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