perf tools: Copy metric events properly when expand cgroups

The metricgroup__copy_metric_events() is to handle metrics events when
expanding event for cgroups.  As the metric events keep pointers to
evsel, it should be refreshed when events are cloned during the
operation.

The perf_stat__collect_metric_expr() is also called in case an event has
a metric directly.

During the copy, it references evsel by index as the evlist now has
cloned evsels for the given cgroup.

Also kernel test robot found an issue in the python module import so add
empty implementations of those two functions to fix it.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200924124455.336326-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/python.c

@@ -15,6 +15,8 @@
 #include "thread_map.h"
 #include "trace-event.h"
 #include "mmap.h"
+#include "stat.h"
+#include "metricgroup.h"
 #include "util/env.h"
 #include <internal/lib.h>
 #include "util.h"
@@ -60,6 +62,23 @@ int parse_callchain_record(const char *arg __maybe_unused,
  */
 struct perf_env perf_env;
 
+/*
+ * Add this one here not to drag util/stat-shadow.c
+ */
+void perf_stat__collect_metric_expr(struct evlist *evsel_list)
+{
+}
+
+/*
+ * Add this one here not to drag util/metricgroup.c
+ */
+int metricgroup__copy_metric_events(struct evlist *evlist, struct cgroup *cgrp,
+				    struct rblist *new_metric_events,
+				    struct rblist *old_metric_events)
+{
+	return 0;
+}
+
 /*
  * Support debug printing even though util/debug.c is not linked.  That means
  * implementing 'verbose' and 'eprintf'.