perf evsel: Refactor tool events

Tool events unnecessarily open a dummy perf event which is useless
even with `perf record` which will still open a dummy event. Change
the behavior of tool events so:

 - duration_time - call `rdclock` on open and then report the count as
   a delta since the start in evsel__read_counter. This moves code out
   of builtin-stat making it more general purpose.

 - user_time/system_time - open the fd as either `/proc/pid/stat` or
   `/proc/stat` for cases like system wide. evsel__read_counter will
   read the appropriate field out of the procfs file. These values
   were previously supplied by wait4, if the procfs read fails then
   the wait4 values are used, assuming the process/thread terminated.
   By reading user_time and system_time this way, interval mode, per
   PID and per CPU can be supported although there are restrictions
   given what the files provide (e.g. per PID can't be combined with
   per CPU).

Opening any of the tool events for `perf record` is changed to return
invalid.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Weilin Wang <weilin.wang@intel.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: James Clark <james.clark@arm.com>
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: Ze Gao <zegao2021@gmail.com>
Cc: Song Liu <song@kernel.org>
Cc: Leo Yan <leo.yan@linux.dev>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240503232849.17752-1-irogers@google.com