[Backport 2.x] Implementing pagination for _cat/shards (#14641)

[gargharsh3134]

• Adding _list/shards API

Description

Manually backporting #14641 to 2.x.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

✅ Gradle check result for fb7250c: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 78.82353% with 54 lines in your changes missing coverage. Please review.

Project coverage is 71.79%. Comparing base (96fdbfd) to head (fb7250c).
Report is 2 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...admin/cluster/shards/TransportCatShardsAction.java	0.00%	20 Missing ⚠️
...g/opensearch/rest/action/cat/RestShardsAction.java	41.17%	10 Missing ⚠️
...a/org/opensearch/action/pagination/PageParams.java	75.00%	1 Missing and 5 partials ⚠️
...rch/action/pagination/IndexPaginationStrategy.java	78.26%	0 Missing and 5 partials ⚠️
...va/org/opensearch/action/pagination/PageToken.java	75.00%	1 Missing and 4 partials ⚠️
...action/admin/cluster/shards/CatShardsResponse.java	81.81%	2 Missing and 2 partials ⚠️
...rch/action/pagination/ShardPaginationStrategy.java	95.55%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #16396      +/-   ##
============================================
- Coverage     71.81%   71.79%   -0.03%     
- Complexity    65052    65158     +106     
============================================
  Files          5305     5307       +2     
  Lines        304143   304341     +198     
  Branches      44231    44270      +39     
============================================
+ Hits         218418   218489      +71     
- Misses        67527    67661     +134     
+ Partials      18198    18191       -7     

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