[Tiered Cache] Use ConcurrentHashMap explicitly in IndicesRequestCache

[kiranprakash154]

Description

@andrross commented on PR - https://github.com/opensearch-project/OpenSearch/pull/14221/files to use ConcurrentHashMap explicitly instead of ConcurrentMap since ConcurrentHashMap gives stronger guarantees than other implementations of ConcurrentMap.

Though Like @sohami pointed out ConcurrentCollections.newConcurrentMap(); returns a new ConcurrentHashMap, having stronger type safety will guarantee and safeguard against future changes.

    public static <K, V> ConcurrentMap<K, V> newConcurrentMap() {
        return new ConcurrentHashMap<>();
    }

Below is the screenshot of the comment - link

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 30a95a5: FAILURE

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[github-actions]

❌ Gradle check result for 8a949d4: FAILURE

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[github-actions]

❕ Gradle check result for 5a56ec1: UNSTABLE

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

[github-actions]

❌ Gradle check result for 256e7ea: FAILURE

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[kiranprakash154]

❌ Gradle check result for 8a949d4: 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?

Test Result (no failures)

[kiranprakash154]

❕ Gradle check result for 5a56ec1: UNSTABLE

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

#9859
#14304

[github-actions]

❌ Gradle check result for 256e7ea: 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]

✅ Gradle check result for 40f0269: SUCCESS

[kiranprakash154]

@andrross can you merge this ? Thanks !