perf pmu: Abstract alias/event struct

In order to be able to lazily compute aliases/events for a PMU, move
the struct perf_pmu_alias into pmu.c.

Add perf_pmu__find_event and perf_pmu__for_each_event that take a
callback that is called for the found event or for each event.

The layout of struct pmu and the event/alias list is unchanged but the
API is altered so that aliases are no longer directly accessed, allowing
for later changes.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230824041330.266337-3-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>