perf tools report: Add custom scripts to script menu

Add a way to define custom scripts through ~/.perfconfig, which are then
added to the scripts menu. The scripts get the same arguments as 'perf
script', in particular -i, --cpu, --tid.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20190311144502.15423-10-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>