LPBackendDictionary - a debugging view of a MIP backend connected to interactive_simplex_method

[mkoeppe]

This is a follow-up on #18734.

This ticket creates:

• a new class, LPBackendDictionary (inheriting from LPAbstractDictionary), would avoid going through InteractiveLP and rather be tied directly to the MILP backend, using tableau data query functions such as getBInvArow etc.

(It would be in a separate file perhaps interactive_backend_dictionary.py, so as not to add clutter to the didactical implementation in interactive_simplex_method.py.)

#18732 added most of the missing functions for retrieving the data of the dictionary (for the GLPK backend) such as getBInvARow etc. (#18763 does the same for the COIN backend.) #18733 provides a common interface and corresponding MixedIntegerLinearProgram methods.

Doctests could then test that:

• A backend has implemented all the necessary methods to get tableau information.
• The information is consistent, by checking that the LPBackendDictionary (in this ticket) and the LPDictionary (created in #18734) are the same.