perf pmu: Merge JSON events with sysfs at load time

perf pmu: Merge JSON events with sysfs at load time

Rather than load all sysfs events then parsing all JSON events and
merging with ones that already exist. When a sysfs event is loaded, look
for a corresponding JSON event and merge immediately.

To simplify the logic, early exit the perf_pmu__new_alias function if an
alias is attempted to be added twice - as merging has already been
explicitly handled.

Fix the copying of terms to a merged alias and some ENOMEM paths.

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/20230824041330.266337-12-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>