Interface SCIP methods

[adamj34]

Adds the following methods:
getNNodesLeft(), getNRuns(), getNReoptRuns(), addNNodes(), getDeterministicTime(), getAvgDualbound(), getMaxTotalDepth(), getNBacktracks(), getFocusNode(), getAvgLowerbound(), getFirstPrimalBound(), getLowerboundRoot(), getUpperbound(), getNObjlimLeaves()

Adds tests in tests/test_statistics.py for migrated methods

Adds function signatures to scip.pyi for hints

Updates CHANGELOG.md

[adamj34]

@Joao-Dionisio were there some changes in the ruff config? I didn't even touch these lines in my commits.

If it's ok I can refactor it to use the more modern X | Y syntax as suggested in the error message

[Joao-Dionisio]

This is likely just a new ruff version flagging some errors. I'd just merge without caring much about this, but if you're offering to fix this, I'm more than happy to accept :)

I'll take a little bit to review, but everything seems to be in order. Can you please make sure that the optimized_model() manages to find primal solutions?

[adamj34]

I checked that optmized_model() wasn't able to find any primal solution, so I 've increased the node limit parameter and now it finds 1.

Regarding the X | Y syntax, I only changed it in scip.pyi to pass the pipeline checks and because this syntax is already used there.

I was thinking about replacing typing.Union in the entire repo, but in general such fixes are considered unsafe for Python versions prior to 3.10 (see for reference: https://docs.astral.sh/ruff/rules/non-pep604-annotation-union/) and pyproject.toml only requires python>=3.8. Maybe there's no point in touching it until the project moves to python>=3.10?