perf trace: Move msg_flags beautifier to tools/perf/trace/beauty/

To reduce the size of builtin-trace.c.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-11zxg3qitk6bw2x30135k9z4@git.kernel.org


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