Merge branch 'bpf: remove bpf_load loader completely'

"Daniel T. says:

====================

Numerous refactoring that rewrites BPF programs written with bpf_load
to use the libbpf loader was finally completed, resulting in BPF
programs using bpf_load within the kernel being completely no longer
present.

This patchset refactors remaining bpf programs with libbpf and
completely removes bpf_load, an outdated bpf loader that is difficult
to keep up with the latest kernel BPF and causes confusion.

Changes in v2:
 - drop 'move tracing helpers to trace_helper' patch
 - add link pinning to prevent cleaning up on process exit
 - add static at global variable and remove unused variable
 - change to destroy link even after link__pin()
 - fix return error code on exit
 - merge commit with changing Makefile

Changes in v3:
 - cleanup bpf_link, bpf_object and cgroup fd both on success and error
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>