ci: install pytest-rerunfailures where needed; add retry config to test-cov script
#297
| Job | Run time |
|---|---|
| 1m 45s | |
| 1m 36s | |
| 2m 46s | |
| 3m 7s | |
| 1m 9s | |
| 1m 5s | |
| 11m 28s |