Adjust nice values to 0

[cp-elastic]

Release notes

• Adjusts the Logstash process nice value from 19 to 0 to be more in line with standard practices

What does this PR do?

Fixes #19189
Adjusts the Logstash process nice value from 19 to 0 to be more in line with standard practices.

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

Prevents Logstash from being silent performance bottleneck when deployed on a system with competing services.
Troubleshooting Logstash typically overlooks this nice value override, and there are no obvious signs that this is the cause of Logstash's performance being impacted.

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

Related issues

Use cases

Screenshots

Logs

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)
• run exhaustive tests : Run the exhaustive tests Buildkite pipeline.

[mergify]

This pull request does not have a backport label. Could you fix it @cp-elastic? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label

[github-actions]

🔍 Preview links for changed docs

• docs/reference/performance-troubleshooting.md

[github-actions]

✅ Elastic Docs Style Checker (Vale)

No issues found on modified lines!

---

The Vale linter checks documentation changes against the Elastic Docs style guide. To use Vale locally or report issues, refer to Elastic style guide for Vale.

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: c8ab13c