laplace is again proceeding to code generation

UFL did not like  my way of replacing some args with 1 as it
destroyed the shape information. It now remains in the expression,
but triggers code generation separately.

and remove old implementation

much more clever!

islpy installation seems fundamentally broken. So, this is a
workaround to still be able to automatically sandbox it.

... to later insert analysis/feedback loop

in cgen and from the cache.