Remove experimental symmetry breaker (#4005)

Remove experimental symmetry breaker (#4005)

This never impacted performance positively. Fixes #3997 and fixes #4015.

There was a folder that the symmetry breaker was used on regress1/sym. These are simple examples that show when it is possible to find symmetries in SMT; the symmetry breaker is not critical for solving these. For now I'm leaving them as regressions documenting possible benchmarks to target if we revisit this technique.