perf trace: Add array of chars scnprintf beautifier

perf trace: Add array of chars scnprintf beautifier

Needed for sched's traceoints prev/next comm, where, unlike with
syscalls, we are not dealing with an integer or pointer, but an array
straight out from the ring buffer.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-rlll7tmcqe1g4odtaifil5re@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>