perf ui browser: Move the extra title lines from the hists browser

This will be useful for the annotate browser as well, that wants to have
extra title lines, i.e. the current ui_browser unconditionally reserves
the first line for a browser title and the last one for status messages.

But some browsers, like the buckets one (hists browser) needs extra
lines to show headers, allowing it to be shown or not, press 'H' in
'perf top' or 'perf report' to see this feature.

So move that logic to the core ui_browser used by the hists_browser
('perf top' and 'perf report' main interface) so that it can be used by
the annotate browser too.

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-r38xm3ut37ulbg1o5tn5iise@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>