Merge branch 'veristat: further usability improvements'

Andrii Nakryiko says:

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

A small patch set adding few usability improvements and features making
veristat a more convenient tool to be used for work on BPF verifier:

  - patch #2 speeds up and makes stats parsing from BPF verifier log more
    robust;

  - patch #3 makes veristat less strict about input object files; veristat
    will ignore non-BPF ELF files;

  - patch #4 adds progress log, by default, so that user doing
    mass-verification is aware that veristat is not stuck;

  - patch #5 allows to tune requested BPF verifier log level, which makes
    veristat a simplest way to get BPF verifier log, especially successfully
    verified ones.

v1->v2:
  - don't emit progress in non-table mode, as it breaks CSV output.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>