Rename it to hists_browser__scnprintf_title() to better reflect that it
provides a scnprintf-like function operating on a hists_browser
instance.

This paves the way to have a non-hists_browser specific function to
scnprintf format a title with per evsel information to use in other
tools or UIs.

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-sntpyzxsnme9jvuz2qntwoh2@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>