Add a slim Docker image for testing

[MrAlias]

For testing purposes we only need the auto-instrumentation code (not tests, examples, docs, etc.). Add an equivalent Dockerfile to the base one that will exclude all these extraneous items.

[RonFed]

Do we have a reason to include examples/tests/licenses in the main image?
All those exclusions looks valid to me also for the main image

[MrAlias]

Do we have a reason to include examples/tests/licenses in the main image? All those exclusions looks valid to me also for the main image

I guess the final image is just a thin distroless base image with the binary copied to it. No reason to copy everything there.

That said, I think we do need to update our final image to contain the licenses for legal reasons.

I can look into updating.

[MrAlias]

Do we have a reason to include examples/tests/licenses in the main image? All those exclusions looks valid to me also for the main image

I plan to address this in a separate PR. The test Dockerfile is distinct enough in that it does not generate builds for non-native architectures that it cannot be unified into a single image.

I plan to move forward with adding a separate test image and clean up the main build image.

[RonFed]

@MrAlias generating the ebpf .go and .o files inside a container has a big advantage that is produces a consistent result. It is also recommended by the cilium ebpf library.

Regardless of this, what is the motivation to generate the files outside of the container? Is it to save time in the tests?