add solver binaries to the release artifacts

[charles-cooper]

it can be a bit cumbersome to get the solver binaries, especially bitwuzla. a fairly easy way to address this would be to just include the binaries in the github release artifacts, that way if the user doesn't have it another way they can just copy the binary to somewhere in their path.

[msooseth]

I need the help of Lexi about this, as it's a bit of a conceptual change. I think it's actually sane to add them, but also, they are kind of supposed to be built by the respective maintainers. However, especially bitwuzla is difficult to obtain. As mentioned, I have reached out to the bitwuzla developers, and they promised to consider including the build that Charles generously donated. I'll ask Lexi what to do once they are back! I fear that we'll release one more hevm without the solver binaries in the meanwhile.