feat: improve s3 access log parsing along with documentation updates

[Kavindu-Dodan]

Proposed commit message

• Improve Firehose log stream detection for S3 access logs based on this remark - [AWS Firehose] Non-S3 logs are incorrectly classified as aws.s3access #15157 (comment)
• Add compute checksum example to integration tests ¹
• Improve Firehose integration documentation to highlight installation is only for assets

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices

How to test this PR locally

• Build package and deploy to see rendered documentation
• Run integration tests to see correct log stream detection

Related issues

Fixes #15157

Screenshots

Improved documentation to highlight firehose integration only need asset intallation,

Footnotes

1. https://docs.aws.amazon.com/AmazonS3/latest/userguide/LogFormat.html ↩

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
90.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[elasticmachine]

💚 Build Succeeded

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