Nothing happens on setting constant through set_constant method

[har-gup]

Here is the sample project which is reproducing the problem: https://github.com/har-gup/rhea-constant-issue.

The same issue doesn't happen if we use edit variable in a constraint instead of constant.
I tried debugging the issue, and saw that set_constant_ method is returning from https://github.com/Nocte-/rhea/blob/0.3/rhea/simplex_solver.cpp#L184 without adding any row to infeasible_rows_, and therefore dual_optimize function is not called.

@Nocte- If we change following lines https://github.com/Nocte-/rhea/blob/0.3/rhea/simplex_solver.cpp#L164 and https://github.com/Nocte-/rhea/blob/0.3/rhea/simplex_solver.cpp#L202 to
auto delta = -(constant - evs.prev_constant);, and expr.add(expr.coefficient(evs.marker) * delta); respectively, the way it is in suggest_value_ function https://github.com/Nocte-/rhea/blob/0.3/rhea/simplex_solver.cpp#L265 then it works fine.

[har-gup]

@Nocte- Please see whether the fix I suggested above is fine?