perf parse-events: Avoid scanning PMUs that can't contain events

Add perf_pmus__scan_for_event that only reads sysfs for pmus that
could contain a given event.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250624231837.179536-2-irogers@google.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>