perf test cpumap: Avoid use-after-free following merge

perf test cpumap: Avoid use-after-free following merge

Previously cpu maps in the test weren't modified by calls to the cpu map
API, however, perf_cpu_map__merge was modified so the left hand argument
was updated.

In the test this meant the maps copy of the "two" map was put/deleted in
the merge meaning when accessed via maps, the pointer was stale and to
the put/deleted memory.

To fix this add an extra layer of indirection to the maps array, so the
updated value of two is accessed.

Fixes: a9d2217556f7745e ("libperf cpumap: Refactor perf_cpu_map__merge()")
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250108051511.1720369-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>