feat: download opentelemetry jar outside of Dockerfile

[paullatzelsperger]

WHAT

Downloads the OpenTelemetry Agent jar "outside" of the Dockerfile. This is actually done in two locations:

1. the build.gradle.kts file: a Gradle task is added for this
2. the publish-docker-image action: a GH Actions step is added, because when publishing we don't use the Gradle Docker task

WHY

Downloading the OTEL Agent inside Docker required adding curl first, and due to security restrictions that required a fixed version. APK, Alpine Linux's package manager, seems to not keep older versions around, which caused the build to break whenever a new version of curl was released.

FURTHER NOTES

• Docker can't use resources outside of its build context, that is why the Gradle task downloads the opentelemetry-javaagent.jar once per project, directly to each project's build/ folder.

Closes #686

[sonarqubecloud]

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0 Bugs
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