Improved RedisCluster's reinitialize_steps and documentation

[barshaul]

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.

1. RedisCluster's reinitialize_steps have been refactored to moved_reinitialize_steps and the documentation has been improved
2. Destructor added to ClusterNode to close connection pool when deleted
3. Added a check to make sure the startup nodes have cluster mode enabled

[codecov-commenter]

Codecov Report

Merging #1765 (bf1d282) into master (d4a9825) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1765      +/-   ##
==========================================
+ Coverage   92.00%   92.05%   +0.04%     
==========================================
  Files          74       74              
  Lines       15617    15633      +16     
==========================================
+ Hits        14369    14391      +22     
+ Misses       1248     1242       -6     

Impacted Files	Coverage Δ
tests/test_connection_pool.py	94.54% <ø> (ø)
redis/cluster.py	90.35% <100.00%> (+0.56%)	⬆️
tests/test_cluster.py	97.39% <100.00%> (+0.01%)	⬆️
tests/conftest.py	92.85% <0.00%> (+1.02%)	⬆️

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[chayim]

See changes