Fix explanation message for TargetPoolAllocationDecider

[bugmakerrrrrr]

Description

[Describe what this change achieves]
TargetPoolAllocationDecider doesn't use correct format when return Decision, resulting in an explanation message that reads something like Routing pools are incompatible. Shard pool: [{}], Node Pool: [{}] without [{}] role.

Related Issues

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

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 dc6b61e

Incompatible components

Skipped components

Compatible components

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

[github-actions]

❕ Gradle check result for dc6b61e: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.remotestore.RemoteIndexPrimaryRelocationIT.testPrimaryRelocationWhileIndexing

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (21c0597) 71.28% compared to head (dc6b61e) 71.37%.
Report is 12 commits behind head on main.

Files	Patch %	Lines
...va/org/opensearch/repositories/s3/S3BlobStore.java	50.00%	3 Missing ⚠️
...a/org/opensearch/repositories/s3/S3Repository.java	50.00%	2 Missing ⚠️
...ch/repositories/s3/async/AsyncTransferManager.java	75.00%	1 Missing and 1 partial ⚠️
...s/replication/SegmentReplicationTargetService.java	92.85%	0 Missing and 2 partials ⚠️
...rg/opensearch/repositories/s3/S3BlobContainer.java	96.55%	0 Missing and 1 partial ⚠️
...earch/repositories/s3/async/AsyncPartsHandler.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #11449      +/-   ##
============================================
+ Coverage     71.28%   71.37%   +0.09%     
- Complexity    59033    59095      +62     
============================================
  Files          4893     4893              
  Lines        277753   277834      +81     
  Branches      40357    40367      +10     
============================================
+ Hits         197989   198316     +327     
+ Misses        63288    63025     -263     
- Partials      16476    16493      +17     

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