Replace mip package with pulp

[kevalmorabia97]

Replace mip package with more popular pulp package for puzzle mip solving. Both use the CBC solver under the hood

Testing

• TODO

[kevalmorabia97]

Review from from author of Pulp package

the PR looks ok.
Not incorrect, but I would not use the variable.varValue property. I usually use pulp.value function.
Check some of the examples to get other insights on style: https://github.com/coin-or/pulp/tree/master/examples
You should get the same (optimal) solution if the model is the same. Regardless of the modeler (python-mip vs pulp) and solver (cbc, gurobi, highs, cplex, etc.).