polys: MPContext.almosteq() should work even if tolerance is disabled
integrals: Added an assertion to ratint_logpart()
polys: Raise an exception if division algorithms don't reduce degree
polys: Added `tolerance` argument to PolyElement.almosteq()
polys: Disabled automatic reduction to zero in RR and CC
integrals: Added a test for a failing integral from PR#2126