Extract pipeline package out of ebpf package

Today we have all pipeline related logic as part of the ebpf package.
Since ebpf package should handle ebpf related stuff (programs, maps, perf/ring buffers), it makes sense to extract the pipeline related logic out of it. This includes event's decoding, enrichment, processing etc.

Start by mapping the pipeline-related logic currently inside the ebpf package, including event decoding, enrichment, and processing. Done means that pipeline logic is extracted from ebpf while ebpf retains responsibility for programs, maps, and perf/ring buffers, with behavior preserved.

Written by the indexing model from the issue text.