perf bench evlist-open-close: Switch user option to use BPF filter

perf bench evlist-open-close: Switch user option to use BPF filter

Finding user processes by scanning /proc is inherently racy and
results in perf_event_open failures. Use a BPF filter to drop samples
where the uid doesn't match.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250604174545.2853620-9-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>