leaking_addresses: add summary reporting options

Currently script just dumps all results found. Potentially, this risks
losing single results among multiple duplicate results. We need some
way of restricting duplicates to assist users of the script. It would
also be nice if we got a report instead of raw results.

Duplicates can be defined in various ways, instead of trying to find a
single perfect solution we can present the user with various options to
display the output. Doing so will typically lead to users wanting to
view the output multiple times. Currently we scan the kernel each time,
this is slow and unnecessary. We can expedite the process by writing the
results to file for subsequent viewing.

Add command line options to enable summary reporting, including options
to write to and read from file.

Signed-off-by: Tobin C. Harding <me@tobin.cc>