add OpenTelemetry to nginx base image

[dmathieu]

I'm splitting this from #7621 so the image can be built and releases independently from the rest of the code changes.

This adds OpenTelemetry CPP and the nginx module to the docker image so it can be used by the controller later.

S390x is skipped, because the GRPC package has been removed from the alpine image, so we can't install the required dependencies.

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[rikatz]

/assign

[rikatz]

So, if someone is using s390x, Opentelemetry wont be available right?

What is the alternative in this case, assuming we want to remove the other telemetry things in a future and use only OTEL?

[rikatz]

Oh, another thing I've been thinking is about splitting the extra bigger modules from the main nginx build image, and let me explain:

Today we take a HUGE amount of time to rebuild nginx base images, even if we are just patching something in openresty. This is mostly due to opentelemetry/opentracing/modsecurity builds.

As all of those are dynamic nginx modules, I think it would be cool if we could just build those images as separate process (download the same nginx source, and build just a container with those modules) and then, during deployment users willing to enable those modules should add those as sidecars.

I did some experiments in #7593 but this need some simplifying.

Will think about that for future modules.

[dmathieu]

Unfortunately, until S390X has support for GRPC in alpine, I'm afraid there isn't much we'll be able to do, outside maybe of using Ubuntu for that platform.

I definitely get the need for a speedier build system, especially since not every module needs to be built every time.

[rikatz]

/lgtm
/approve
Thanks

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dmathieu, rikatz

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