[Backport 2.x] Adding configurable connection count setting for S3 Sync Client (#12028)

[gbbafna]

• Adding configurable connection count setting for S3 Sync Client

• Address PR Comments

• Increase number of connections to 500

---

Description

1. Add configurable S3 plugin's setting max_sync_connections for sync client's max connections.
2. Uses existing setting connection_acquisition_timeout for sync client as well . Today it is only used in async client.

Related Issues

Resolves #12027

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• Public documentation issue/PR created

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[github-actions]

Compatibility status:

Checks if related components are compatible with change 208e36e

Incompatible components

Incompatible components: [https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/performance-analyzer-rca.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/alerting.git]

[github-actions]

✅ Gradle check result for 208e36e: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (179d2d4) 71.09% compared to head (208e36e) 71.19%.
Report is 1 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #12053      +/-   ##
============================================
+ Coverage     71.09%   71.19%   +0.10%     
- Complexity    59394    59458      +64     
============================================
  Files          4891     4891              
  Lines        279974   279982       +8     
  Branches      41070    41070              
============================================
+ Hits         199050   199345     +295     
+ Misses        63994    63737     -257     
+ Partials      16930    16900      -30     

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