This is preparation for exporting rusage values as tool events.

Add new global stats tracking the values obtained via rusage.

For now only ru_utime and ru_stime are part of the tracked stats.

Both are stored as nanoseconds to be consistent with 'duration_time',
although the finest resolution the struct timeval data in rusage
provides are microseconds.
Signed-off-by: Florian Fischer <florian.fischer@muhq.space>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220420102354.468173-2-florian.fischer@muhq.spaceSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>