selftests/bpf: Test bpf_mprog query API via libbpf and raw syscall

selftests/bpf: Test bpf_mprog query API via libbpf and raw syscall

Add a new test case which performs double query of the bpf_mprog through
libbpf API, but also via raw bpf(2) syscall. This is testing to gather
first the count and then in a subsequent probe the full information with
the program array without clearing passed structs in between.

  # ./vmtest.sh -- ./test_progs -t tc_opts
  [...]
  ./test_progs -t tc_opts
  [    1.398818] tsc: Refined TSC clocksource calibration: 3407.999 MHz
  [    1.400263] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fd336761, max_idle_ns: 440795243819 ns
  [    1.402734] clocksource: Switched to clocksource tsc
  [    1.426639] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.428112] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  #252     tc_opts_after:OK
  #253     tc_opts_append:OK
  #254     tc_opts_basic:OK
  #255     tc_opts_before:OK
  #256     tc_opts_chain_classic:OK
  #257     tc_opts_chain_mixed:OK
  #258     tc_opts_delete_empty:OK
  #259     tc_opts_demixed:OK
  #260     tc_opts_detach:OK
  #261     tc_opts_detach_after:OK
  #262     tc_opts_detach_before:OK
  #263     tc_opts_dev_cleanup:OK
  #264     tc_opts_invalid:OK
  #265     tc_opts_max:OK
  #266     tc_opts_mixed:OK
  #267     tc_opts_prepend:OK
  #268     tc_opts_query:OK            <--- (new test)
  #269     tc_opts_replace:OK
  #270     tc_opts_revision:OK
  Summary: 19/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20231006220655.1653-4-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>