Enable Simplify API for Bitwuzla

[baierd]

Bitwuzla supports simplification of formulas via the simplify() call. We should enable this in our wrapper for the next update of Bitwuzla.

[daniel-raffler]

I've opened a new branch and removed simplify() from the ignore list. We still need to decide when to call this method. According to the API documentation (link):

Each call to Bitwuzla::check_sat() simplifies the input formula as a preprocessing step. It is not necessary to call this function explicitly in the general case.

However, there may still be some exceptions?