OCSP Stapling Support

[chayim]

Pull Request check-list

Please make sure to review and check all of these items:

• Does $ tox pass with this change (including linting)?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

Please provide a description of the change here.

[codecov-commenter]

Codecov Report

Merging #1873 (068b71c) into master (15f315a) will decrease coverage by 0.63%.
The diff coverage is 7.63%.

@@            Coverage Diff             @@
##           master    #1873      +/-   ##
==========================================
- Coverage   93.60%   92.97%   -0.64%     
==========================================
  Files          76       76              
  Lines       16214    16389     +175     
==========================================
+ Hits        15177    15237      +60     
- Misses       1037     1152     +115     

Impacted Files	Coverage Δ
redis/client.py	89.37% <ø> (ø)
redis/ocsp.py	0.00% <0.00%> (ø)
setup.py	0.00% <ø> (ø)
tests/test_ssl.py	48.46% <19.04%> (-5.67%)	⬇️
redis/connection.py	86.78% <28.57%> (-1.56%)	⬇️
tests/conftest.py	88.73% <0.00%> (-0.91%)	⬇️
tests/test_cluster.py	98.16% <0.00%> (-0.38%)	⬇️
tests/test_search.py	99.07% <0.00%> (+0.05%)	⬆️
redis/cluster.py	92.42% <0.00%> (+0.37%)	⬆️
... and 2 more

---

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[whardier]

Is there any specific reason pyopenssl is pinned in setup.py?