Add counting.py - a python version of counting.c to demonstrate
measuring and reading of counts for given perf events.

Committer testing:

Build perf and make the generated python binding somewhere you can point
to to avoid using the one in the distro python3-perf (fedora, may be
different in other distros):

  $ make -k O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin

Copy /tmp/build/perf-tools-next/python/perf.cpython-313-x86_64-linux-gnu.so to
somewhere outside this toolbox container and then use it with root:

  # export PYTHONPATH=/root/python/
  # ls -la /root/python/
  total 10640
  drwxr-xr-x. 1 root root       72 May 21 11:40 .
  dr-xr-x---. 1 root root      574 May 21 11:40 ..
  -rwxr-xr-x. 1 acme acme 10894360 May 21 11:40 perf.cpython-313-x86_64-linux-gnu.so
  # tools/perf/python/counting.py | head -5
  For evsel(software/cpu-clock/) val: 2930946 enable: 2932479 run: 2932479
  For evsel(software/cpu-clock/) val: 2924975 enable: 2926267 run: 2926267
  For evsel(software/cpu-clock/) val: 2921017 enable: 2922430 run: 2922430
  For evsel(software/cpu-clock/) val: 2914966 enable: 2916549 run: 2916549
  For evsel(software/cpu-clock/) val: 2910027 enable: 2911589 run: 2911589
  #

Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
[ make the API take a CPU and thread then compute from these the appropriate indices. ]
Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/linux-perf-users/CAP-5=fWb-=hCYmpg7U5N9C94EucQGTOS7YwR2-fo4ptOexzxyg@mail.gmail.com/
Link: https://lore.kernel.org/r/20250519195148.1708988-8-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>