Add support for CLUSTER SHARDS

[dvora-h]

Pull Request check-list

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• 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)?
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Description of change

closes #2120

[chayim]

Tiny nit of a request on doc-ing. Looks great otherwise!!!

[codecov-commenter]

Codecov Report

Merging #2151 (d32291a) into master (e1988c6) will decrease coverage by 0.09%.
The diff coverage is 17.85%.

@@            Coverage Diff             @@
##           master    #2151      +/-   ##
==========================================
- Coverage   92.29%   92.19%   -0.10%     
==========================================
  Files         105      105              
  Lines       25244    25274      +30     
==========================================
+ Hits        23298    23302       +4     
- Misses       1946     1972      +26     

Impacted Files	Coverage Δ
redis/cluster.py	90.31% <7.14%> (-1.42%)	⬇️
tests/test_cluster.py	96.96% <25.00%> (-0.64%)	⬇️
redis/commands/cluster.py	92.95% <50.00%> (-0.62%)	⬇️
tests/test_asyncio/test_search.py	98.35% <0.00%> (-0.33%)	⬇️
tests/test_graph.py	90.68% <0.00%> (+0.06%)	⬆️
redis/asyncio/connection.py	84.83% <0.00%> (+0.11%)	⬆️

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