Fix s3 input when there is a blank line in the log file

[kaiyan-sheng]

What does this PR do?

When there is an empty line in a log file, s3 input shouldn't abort the rest of the file. This PR is to skip the empty line and continue to ingest the rest of the log file.

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.

Related issues

• Closes S3 collector aborts when there is a blank line in the log file #24872

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[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 s3_input_skip_line upstream/s3_input_skip_line
git merge upstream/master
git push upstream s3_input_skip_line

[elasticmachine]

💚 Build Succeeded

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Build stats

• Build Cause: Pull request #25357 updated

• Start Time: 2021-04-28T20:29:33.437+0000

• Duration: 105 min 11 sec

• Commit: f03bb15

Test stats 🧪

Test	Results
Failed	0
Passed	7009
Skipped	1193
Total	8202

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💚 Flaky test report

Tests succeeded.

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Test stats 🧪

Test	Results
Failed	0
Passed	7009
Skipped	1193
Total	8202

[ChrsMark]

Please resolve the conflict before merging.

[kaiyan-sheng]

/test