Christmas issues

[LKlinke]

• Adapt the benchmark script to handle invariant files #53
• Refactor Example Structure (EVT_inv -> invariant synthesis, loop_equivalence -> equivalence [subfolder loopy, loop-free])
• Refactor check_equivalence(...) to actually check equivalence of two programs, not just loop + invariant.
• Write test cases for the refactored equivalence check
• Develop new loop-free benchmarks for the equivalence check
• identify bugs in Invariant Synthesis (adding issues, resolving them as far as possible)

Due date: 22.01.2025