Merge branch 'veristat: CSV output, comparison mode, filtering'

Andrii Nakryiko says:

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

Add three more critical features to veristat tool, which make it sufficient
for a practical work on BPF verifier:

  - CSV output, which allows easier programmatic post-processing of stats;

  - building upon CSV output, veristat now supports comparison mode, in which
    two previously captured CSV outputs from veristat are compared with each
    other in a convenient form;

  - flexible allow/deny filtering using globs for BPF object files and
    programs, allowing to narrow down target BPF programs to be verified.

See individual patches for more details and examples.

v1->v2:
- split out double-free fix into patch #1 (Yonghong);
- fixed typo in verbose flag (Quentin);
- baseline and comparison stats were reversed in output table, fixed that.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/veristat.cfg

+# pre-canned list of rather complex selftests/bpf BPF object files to monitor
+# BPF verifier's performance on
+bpf_flow*
+bpf_loop_bench*
+loop*
+netif_receive_skb*
+profiler*
+pyperf*
+strobemeta*
+test_cls_redirect*
+test_l4lb
+test_sysctl*
+test_tcp_hdr_*
+test_usdt*
+test_verif_scale*
+test_xdp_noinline*
+xdp_synproxy*