perf report/top: Improve toggle callchain menu option

Taking into account the current status of the callchain, i.e. if folded,
show "Expand", otherwise "Collapse", also show the name of the entry
that will be affected and mention the hotkeys for expanding/collapsing
all callchains below the main entry, the one that appears with/without
callchains.

Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-03arm6poo8463k5tfcfp7gkk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>