Dump / restore memory

[trufae]

right now it is possible to dump memory using wtff @@ maps* but this is probably not as peformant and easy as it should, and as long as dumping and restoring process memory for forensics purposes is a very useful operation i think it would make sense to have this primitive operation more accessible and optimized from the agent side doing streaming for raw data instead of going through r2's io

proposals? these commands should be in sync with the dm subcommands in r2. and maybe even make them work seamlessly via debug io plugin