[CRIU] Dump/restore statistics in CRIU

[Pavel Emelyanov]

Hi,

Since today we are going to expose various statistics about dump/restore into
a yet another file. For dump the file is called stats-dump, it's located in
the directory to where images and log files are put, this file is in protobuf
format and can be observed using the "criu show -f" command.

Feel free to extend the stats provided.

Thanks,
Pavel