Merge branch 'fix-bpf-multi-uprobe-pid-filtering-logic'

Andrii Nakryiko says:

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Fix BPF multi-uprobe PID filtering logic

It turns out that current implementation of multi-uprobe PID filtering logic
is broken. It filters by thread, while the promise is filtering by process.
Patch #1 fixes the logic trivially. The rest is testing and mitigations that
are necessary for libbpf to not break users of USDT programs.

v1->v2:
  - fix selftest in last patch (CI);
  - use semicolon in patch #3 (Jiri).
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Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>