Refactor processing of inequalities with oo

fixes #7775
fixes #7798
fixes #7841

this patch replaces #7800 and #7799
These seem wrong to me. `Heaviside(-x - oo)` can only be nonzero if `-x - oo` is positive.

More practically, an expression with DiracDelta really on makes sense as an integrand (at least mathematically), and I suspect expressions with this new term will trip up the integrator.