Merge branch 'libbpf: Streamline internal BPF program sections handling'

Andrii Nakryiko says:

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This small patch set performs internal refactorings around libbpf BPF program
ELF section definitions' handling. This is preparatory changes for further
changes around making libbpf BPF program section handling more strict but also
pluggable and customizable, as part of the libbpf 1.0 effort. See individual
patches for details.
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>