Fix dissect trim panics from DELETE (\u007f) character

[montaguethomas]

What does this PR do?

Fixes an index out of range panic with asciiTrimmer.Trim().

Why is it important?

Should a string begin or end with the DELETE (\u007f)(127) ASCII character (with or without a leading/trailing space), asciiTrimmer.Trim() will throw a panic.

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
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

Run the updated tests without the fix in trim.go.

Related issues

• Closes Dissect trim panics from unicode DELETE (\u007f) char #30657

Logs

panic: runtime error: index out of range [127] with length 127

goroutine 52 [running]:
github.com/elastic/beats/v7/libbeat/processors/dissect.asciiTrimmer.Trim(...)
	/go/src/github.com/elastic/beats/libbeat/processors/dissect/trim.go:66
github.com/elastic/beats/v7/libbeat/processors/dissect.(*Dissector).Dissect(0xc000a0da40, 0xc001517d10, 0xe5, 0x108528980, 0xc0015b1060, 0x0)
	/go/src/github.com/elastic/beats/libbeat/processors/dissect/dissect.go:73 +0x104
github.com/elastic/beats/v7/libbeat/processors/dissect.(*processor).Run(0xc0005b5280, 0xc0015c81c0, 0x107d95b74, 0x1e, 0xc000b8bad0)
	/go/src/github.com/elastic/beats/libbeat/processors/dissect/processor.go:91 +0x3e5

[cla-checker-service]

💚 CLA has been signed

[mergify]

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

• backport-v./d./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

💚 Build Succeeded

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Build stats

• Start Time: 2022-03-15T17:36:59.544+0000

• Duration: 89 min 39 sec

Test stats 🧪

Test	Results
Failed	0
Passed	25714
Skipped	2203
Total	27917

💚 Flaky test report

Tests succeeded.

🤖 GitHub comments

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[montaguethomas]

Seems I do not have permissions to set labels on the PR. Suggest this should be backported.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b bugfix/dissect-trim upstream/bugfix/dissect-trim
git merge upstream/main
git push upstream bugfix/dissect-trim

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b bugfix/dissect-trim upstream/bugfix/dissect-trim
git merge upstream/main
git push upstream bugfix/dissect-trim

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[cmacknz]

/test

[cmacknz]

@adriansr you were the original author here, can you review this fix?

[adriansr]

Thanks a lot for fixing. I'm adding some corrections to the changelog

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b bugfix/dissect-trim upstream/bugfix/dissect-trim
git merge upstream/main
git push upstream bugfix/dissect-trim

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[jlind23]

@adriansr could we please merge it as it has been approved?