[OPIK-8197] [BE] fix: unhang PythonEvaluatorServiceTest and bound every test with a timeout - #8108

 43 files  ± 0   43 suites  ±0   4m 59s ⏱️ + 1m 3s
339 tests ± 0  337 ✅ ± 0  2 💤 ±0  0 ❌ ±0 
339 runs  +23  337 ✅ +23  2 💤 ±0  0 ❌ ±0 

Results for commit b192512. ± Comparison against earlier commit c04d283.