[9.4] (backport #18874) DeadLetterQueueUtils#extractSegmentId improvement: replace split with index of and substring methods.

[mergify]

Release notes

What does this PR do?

DLQ flush operation is heavy, under the hood DeadLetterQueueUtils#extractSegmentId will be called. The String#split is also CPU intensive that internally utilizes Pattern#compile. Since the logic is simple, it can be replaceable with indexOf and substring.

Why is it important/What is the impact to the user?

A bit performance improvement when using DLQ.

Checklist

• My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

Functionality test can be done by enabling DLQ and changing its settings, such as make size small to make DLQ full.
But performance measurement is a bit hard on powerful machines, so here is the benchmark - #18883

Related issues

Use cases

Screenshots

Logs

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This is an automatic backport of pull request #18874 done by [Mergify](https://mergify.com).

[github-actions]

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[mashhurs]

clean backport, will hold merging till gemfile.lock land

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: da91ffd

cc @mashhurs