Add the missing infra code in the perf python bindings for measuring and
reading the counter values for the given perf event. Demonstrate the
usage of this with counting.py - a python version of counting.c

Ian v2 -> v3:
1. Make the read API use CPUs and threads rather than indices as
   discussed in:
https://lore.kernel.org/linux-perf-users/20250512055748.479786-1-gautam@linux.ibm.com/
2. Add python cpus and threads functions to evsel so that these can be
   iterated to avoid reading CPUs not present on a parsed evsel.
3. Clean up bits of the perf_thread_map libperf API.
3. Allow a command line event to be specified for parsing, for example:
```
$ tools/perf/python/counting.py -e data_read
For evsel(uncore_imc_free_running_0/data_read/) val: 23062 enable: 1612523 run: 1612523
For evsel(uncore_imc_free_running_1/data_read/) val: 22423 enable: 1599354 run: 1599354
```

Gautam v1 -> v2:
1. Use the existing iteration support for evlist
2. Drop the use of next method
3. Use existing helper functions for python example

Gautam Menghani (4):
  perf python: Add support for perf_counts_values to return counter data
  perf python: Add evsel read method
  perf python: Add evlist close support
  perf python: Add counting.py as example for counting perf events

Ian Rogers (3):
  libperf threadmap: Don't segv for index 0 for the NULL perf_thread_map
  libperf threadmap: Add perf_thread_map__idx
  perf python: Add evsel cpus and threads functions

 tools/lib/perf/include/perf/threadmap.h |   1 +
 tools/lib/perf/threadmap.c              |  17 +++
 tools/perf/python/counting.py           |  36 +++++
 tools/perf/util/python.c                | 178 +++++++++++++++++++++++-
 4 files changed, 231 insertions(+), 1 deletion(-)
 create mode 100755 tools/perf/python/counting.py

-- 
2.49.0.1101.gccaa498523-goog

Hi Ian,

Thanks for adding the API related changes, LGTM

Thanks,
Gautam