perf hists: Move hists__scnprintf_title() away from the TUI code

The previous patch made this function useful to non-TUI parts of the
tools, but left it where the function from what it was carved, so that
the patch showed more clearly the process.

Now just move it outside the TUI parts so that we can finally use it,
even when the TUI code doesn't get built/linked.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Martin Liška <mliska@suse.cz>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196935
Link: https://lkml.kernel.org/n/tip-hqj7hvcr3mu5lvcqp3cssio6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>