Update Bitwuzla code for new API

[samanthaarcher0]

Add support for the new C++ API of Bitwuzla

[CyanoKobalamyne]

@yoni206 I think this is good to go now, please take a look when you have the chance.

[yoni206]

Thanks for all of this. It looks fine, though I am wondering if this would be a good opportunity to add a corresponding test directory to here https://github.com/stanford-centaur/smt-switch/tree/main/tests (I think bitwuzla is the only solver that doesn't have one, right?)

[CyanoKobalamyne]

I can do that, but this PR is already big enough, so maybe let's merge that separately.

[CyanoKobalamyne]

Actually, what are the solver-specific tests testing that the top-level ones aren't? They mostly just seem a lot older.

[yoni206]

You are right, it is not really related to this PR. Merged.
Also, I actually don't see a real difference between these two types of tests.
For example, the tests inside the solver directories also just create a solver with the factory, nothing more internal than that.
So perhaps we can at some point port these tests into the unit tests. But that's also not related to this PR and is not urgent.

Thanks for updating bitwuzla!

[CyanoKobalamyne]

Yay, of course, thanks for reviewing! And thank you to @samanthaarcher0! :)