[WIP][CWS] remove usage of btf internals

[paulcacheux]

What does this PR do?

With cilium/ebpf#665 merged, we can remove our usage of btf-internals and use cilium/ebpf directly for our CORE/BTF usage.

TODO:

• cleanup the MapCreate mmapable map detection
• load the kernel spec without the cache (merged upstream)

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

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