[release-19.0] [vtctldclient] Add GetShardReplication (#15389)

[vitess-bot]

Description

This is a backport of #15389

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

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Documentation

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• There should be a comment at the top of each new or modified test to explain what the test does.

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Backward compatibility

• Protobuf changes should be wire-compatible.
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• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 24 lines in your changes are missing coverage. Please review.

Project coverage is 67.42%. Comparing base (977b585) to head (aad6ebc).

Files	Patch %	Lines
go/cmd/vtctldclient/command/shards.go	5.26%	18 Missing ⚠️
go/vt/vtctl/grpcvtctldclient/client_gen.go	0.00%	4 Missing ⚠️
go/vt/vtctl/localvtctldclient/client_gen.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-19.0   #15390      +/-   ##
================================================
- Coverage         67.43%   67.42%   -0.01%     
================================================
  Files              1560     1560              
  Lines            192581   192629      +48     
================================================
+ Hits             129858   129873      +15     
- Misses            62723    62756      +33     

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