chore(ci): testing with Python3.10 and ZK 3.5.10, 3.6.3, 3.7.1

[StephenSorriaux]

Why is this needed?

Make sure the lib is working with Python 3.10 and the latest ZK versions (3.5.10, 3.6.3, 3.7.1)

Proposed Changes

• add Python 3.10 in matrix testing
• change ZK 3.5.8 to ZK 3.5.10 in matrix testing
• add ZK 3.6.3 in matrix testing
• add ZK 3.7.1 in matrix testing
• better discover .jar files when building the classpath (could be better though)
• rename test_connection.py to test__connection.py to get it done first (poor way to try to get it less flaky, I confess) and deactivate fail-fast feature in GA to get the tests' flakiness less painful
• add conftest.py to give a way to get ZK logs when test fails (but needs the -s flag in pytest)
• add ZK local session configuration required to get the read only test working for ZK 3.7
• added Python 3.9 and Python 3.10 to setup.cfg

Does this PR introduce any breaking change?

No

[codecov-commenter]

Codecov Report

Base: 94.43% // Head: 94.51% // Increases project coverage by +0.08% :tada:

Coverage data is based on head (80a121c) compared to base (5f7ae48). Patch coverage: 60.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #659 +/- ## ========================================== + Coverage 94.43% 94.51% +0.08% ========================================== Files 56 57 +1 Lines 8367 8399 +32 ========================================== + Hits 7901 7938 +37 + Misses 466 461 -5 ``` | [Impacted Files](https://codecov.io/gh/python-zk/kazoo/pull/659?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk) | Coverage Δ | | |---|---|---| | [kazoo/testing/common.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdGluZy9jb21tb24ucHk=) | `78.78% <28.57%> (-4.66%)` | :arrow_down: | | [kazoo/tests/conftest.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdHMvY29uZnRlc3QucHk=) | `42.85% <42.85%> (ø)` | | | [kazoo/testing/harness.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdGluZy9oYXJuZXNzLnB5) | `98.34% <100.00%> (+0.01%)` | :arrow_up: | | [kazoo/tests/test\_\_connection.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdHMvdGVzdF9fY29ubmVjdGlvbi5weQ==) | `98.14% <100.00%> (ø)` | | | [kazoo/tests/test\_sasl.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdHMvdGVzdF9zYXNsLnB5) | `87.39% <100.00%> (+0.32%)` | :arrow_up: | | [kazoo/recipe/barrier.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vcmVjaXBlL2JhcnJpZXIucHk=) | `97.93% <0.00%> (-1.04%)` | :arrow_down: | | [kazoo/client.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vY2xpZW50LnB5) | `98.41% <0.00%> (-0.16%)` | :arrow_down: | | [kazoo/tests/test\_client.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vdGVzdHMvdGVzdF9jbGllbnQucHk=) | `98.70% <0.00%> (+0.09%)` | :arrow_up: | | [kazoo/recipe/lock.py](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk#diff-a2F6b28vcmVjaXBlL2xvY2sucHk=) | `97.96% <0.00%> (+0.33%)` | :arrow_up: | | ... and [5 more](https://codecov.io/gh/python-zk/kazoo/pull/659/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=python-zk)

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