QPY had a somewhat implicit assumption that most classes can be
reconstructed by doing `type(obj)(*obj.params)`, which `SwitchCaseOp`
very much does not abide by - to do so would compromise more core parts
of how it is meant to function.  This commit puts in a special case so
that instances of `SwitchCaseOp` present their "params" as the
information necessary to reconstruct the op in the above form, rather
than actually using the parameters.  That didn't feel _entirely_
satisfying, but does work fine.