Build Docker image for Splunk Operator

[Kielek]

@jvoravong please review.

You can check the build on my fork https://github.com/Kielek/splunk-otel-dotnet/actions/runs/7059027432/job/19215767446 and test the docker image by ghcr.io/kielek/splunk-otel-dotnet/splunk-otel-dotnet:latest.

Created based on

• https://github.com/open-telemetry/opentelemetry-operator/blob/main/autoinstrumentation/dotnet/Dockerfile
• https://github.com/signalfx/splunk-otel-java/blob/main/Dockerfile-ghcr
• https://github.com/signalfx/splunk-otel-java/blob/main/.github/workflows/publish-docker-image-ghcr.yml

[github-actions]

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[theletterf]

I have read the CLA Document and I hereby sign the CLA

[jvoravong]

That PR mostly looks good to me. Trying to setup a demo or tests using this new docker image today to see if we are missing anything. Will approve or request needed changes after.

[jvoravong]

Didn't find any obvious issues with the Docker image. While I haven't been able to fully test it yet, the changes should be sufficient. LGTM.