[image-provider]: replace bookworm image with nonroot alpine image

[Red-GV]

Changes

This PR updates the image-provider image to use an alpine with that runs as a non-root user. This allows the service to run in an environment which does not allow privileged users.

Merge Requirements

For new features contributions, please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs
• Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

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This differences in image sizes can be documented here.

[julianocosta89]

LGTM, but I won't merge this one now.
I'd like to hear the opinions from @puckpuck and @mviitane.

This PR changes the base image from nginx:1.27.0-otel to nginxinc/nginx-unprivileged:1.27.5-alpine3.21.

Initially I was concerned about it, but when checking Running nginx as a non-root user at https://hub.docker.com/_/nginx I saw they do recommend https://hub.docker.com/r/nginxinc/nginx-unprivileged.

So I'm fine with the change. Any objections?

[Red-GV]

@julianocosta89 One thing I thought of, this might require a Helm chart update after the next release of this image so that the podSecurityContext can be updated.

[Red-GV]

Hello, just a small reminder about this PR @puckpuck @mviitane @julianocosta89

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[rogercoll]

LGTM (In favor of making the demo more light way). Also, as @julianocosta89 mentioned, nginxinc/nginx-unprivileged is the Nginx's recommended image for non root.