Reduce memory use in Bitwuzla

[daniel-raffler]

Hello,
memory usage in Bitwuzla is still relatively high, see the results from here. Some of this is due to how Bitwuzla works, and may be hard to fix. However, we should investigate if there are still any major issues that can be improved

[baierd]

Note: this might also be a CPAchecker issue! We did not verify that it was a pure JavaSMT issue, that is currently just an assumption.