Update user agent

[graphaelli]

Proposed commit message

Update default user agent to distinguish between all beat modes:

• Standalone indicates that the beat is not running under agent.
• Unmanaged indicates that the beat is running under agent but not managed by Fleet.
• Managed indicates that the beat is running under agent and managed by Fleet.

privilege mode information is only exposed under agent

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• 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.

Disruptive User Impact

Users relying on specific user agents could be impacted. We've made no guarantees of stability for those and the only parts that changes are in the comments section.

Author's Checklist

• verify user agent from a standalone agent
• verify user agent from an unmanaged agent
• verify user agent from a managed agent

[github-actions]

🤖 GitHub comments

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Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @graphaelli? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

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
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[elasticmachine]

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

[pierrehilbert]

@graphaelli it looks like I don't have permission to write on your branch so please run make update to make the CI happy by updating NOTICE.txt and go.sum with the up to date information about the elastic-agent-libs

[AndersonQ]

the tests for user agent aren't passing either. Could you check if it's you code or if they need to be updated?

[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 update-user-agent upstream/update-user-agent
git merge upstream/main
git push upstream update-user-agent

[pierrehilbert]

/test

[github-actions]

@Mergifyio backport 9.0 9.1

[mergify]

backport 9.0 9.1

✅ Backports have been created

• #45493 [9.0](backport #45251) Update user agent has been created for branch 9.0 but encountered conflicts
• #45494 [9.1](backport #45251) Update user agent has been created for branch 9.1 but encountered conflicts