CI: Update used actions, cache pip deps, 3.10 tests (#2799)
CI: Update used actions, cache pip deps, 3.10 tests (#2799)

- Allow to manually trigger a the CI from the GitHub UI (workflow_dispatch)
- Update the used actions to actions/checkout@v3, actions/setup-python@v3 and codecov/codecov-action@v2
- Cache pip dependencies
- Run more tests with Python 3.10
- Bit of cleanup
mwaskom/seaborn,mwaskom/seaborn