SCIP IIS with MOI Conflict interface

[matbesancon]

Adding the new IIS feature to compute conflicts.
For now this is quite a hacky path, relying on variable and constraint names to verify whether a constraint or variable is present in the IIS or not
cc @Opt-Mucca

I haven't found any better way to match the IIS sub-SCIP information to the original model so far, I don't think the IIS produces a correspondence map between original and IIS variables / constraints

[matbesancon]

without surprise, CI cannot pass at the moment because of the finding-by-name issue. Depending on how easy it can be worked out, we'll either copy / adapt the test setup by adding names

[Opt-Mucca]

@matbesancon There is a map from the original problem to the IIS subscip. See the struct SCIP_IIS with varsmap and conssmap in struct_iisfinder. That can be used to determine which constraints are in the IIS (I don't think I programmed something in the reverse direction though, i.e., from subscip to original SCIP).

[matbesancon]

unless I missed it, I don't see any methods to access these two hashmaps

[Opt-Mucca]

That was probably laziness on my part......

[matbesancon]

tss tsss
Then we should merge one of the two MRs I opened on SCIP to expose the necessary information. Feel free to chime in on your favorite version