Enable monitoring buffer for elastic-agent (#30471)

[narph]

Backport from elastic/beats#30559

• Enable monitoring buffer for elastic-agent

• Add diagnostics collect support

• Fix typos

• Fix issues

• Fix metrics collection

• Add CHANGELOG

• Update x-pack/elastic-agent/CHANGELOG.next.asciidoc

Co-authored-by: Bryan Clement bclement01@gmail.com

• Remove unused config

• changelog order

Co-authored-by: Bryan Clement bclement01@gmail.com
(cherry picked from commit 0099f5cf517ee03c88c2c33909a178c04329840e)

[mergify]

This pull request does not have a backport label. Could you fix it @narph? 🙏
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 8./d branch. /d is the digit

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

[elasticmachine]

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• Start Time: 2022-03-23T08:35:25.064+0000

• Duration: 33 min 48 sec

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[ph]

The linter warning are valid, we didn't have a linter on beats before that went in, sorry @narph :(

[ph]

This is interesting, I believe this is a real bug, I don't think you need to create zw.Create() with only the metrics/

[michel-laterman]

The documentation for zip states that adding a trailing slash creates a directory: https://pkg.go.dev/archive/zip#Writer.Create

[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 backport-30471 upstream/backport-30471
git merge upstream/main
git push upstream backport-30471

[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 backport-30471 upstream/backport-30471
git merge upstream/main
git push upstream backport-30471

[narph]

@ph most of this PR changes are already merged in d108e49

[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 backport-30471 upstream/backport-30471
git merge upstream/main
git push upstream backport-30471