Document GRPC settings and default values in README

[karenyrx]

Description

Document how the GRPC settings should be used and add the missing grpc.netty.max_msg_size setting to the README. A corresponding PR in the documentation-webste repo will be created later on as well to reflect these changes.

Related Issues

https://github.com/opensearch-project/OpenSearch/issues/16787

Check List

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

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[karenyrx]

Let me know if a changelog entry is required for this. Thanks!

[github-actions[bot]]

:x: Gradle check result for 23c2de6e7df22b1759519236733d147b1b8ee7c2: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:x: Gradle check result for 23c2de6e7df22b1759519236733d147b1b8ee7c2: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions[bot]]

:white_check_mark: Gradle check result for 23c2de6e7df22b1759519236733d147b1b8ee7c2: SUCCESS

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.79%. Comparing base (4d6f8ba) to head (23c2de6). Report is 39 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #18506      +/-   ##
============================================
+ Coverage     72.67%   72.79%   +0.12%     
- Complexity    67881    67967      +86     
============================================
  Files          5516     5516              
  Lines        312443   312443              
  Branches      45360    45360              
============================================
+ Hits         227067   227451     +384     
+ Misses        66893    66455     -438     
- Partials      18483    18537      +54     

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[peterzhuamazon]

Approved but asking @andrross @finnegancarroll to check as well.

Thanks.