[diagnostics] - Update diagnostics socket path to support read-only filesystems

[VihasMakwana]

What does this PR do?

Previously, the diagnostics socket path was hard coded as /usr/share/elastic-agent/edot-diagnostics-extension.sock, which resulted in failed to create listener: read-only file system when being run inside of a container.
This PR updates the diagnostics socket path based on the STATE_PATH environment variable, ensuring the socket is created in a writable state directory.

Why is it important?

Without this change, the collector fails to start in a read-only filesystem because it used to create the socket under /usr/share/elastic-agent or /tmp

Checklist

• I have read and understood the pull request guidelines of this project.
• 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/fragments using the changelog tool
• I have added an integration test or an E2E test

How to test this PR locally

• Build docker image from this PR by running

SNAPSHOT=true EXTERNAL=true PLATFORMS="linux/arm64" PACKAGES=docker DOCKER_VARIANTS=basic mage -v package

• Run

docker run --read-only --rm -e STATE_PATH=/state --mount type=tmpfs,destination=/state docker.elastic.co/elastic-agent/elastic-agent:9.4.0-SNAPSHOT

• Observe the logs. There shouldn't be any runtime failure.
• Optional:
  • You can exec into the container and do ls /state/data. You'll see that the diagnostics socket is present under the directory.

Related issues

• Closes The elasticdiagnostics extension is not compatible with read only file systems #11572

[elasticmachine]

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• Commit: 6dc9228

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History

cc @VihasMakwana

[elasticmachine]

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