Move methods not related to Memory out of RemoteProcessMemory

Move methods not related to Memory out of RemoteProcessMemory

Now that ModelChecker is gone, it's time to move to the next step of cleanup.

The goal is that CheckerSide is in charge of the interaction with the
application process and RemoteProcessMemory is in charge of its memory.

Right now, RemoteProcessMemory does a bit more, as it stores the pid
and whether or not the application process is running.

This is bad because we want to make RemoteProcessMemory optional, only
used when we need to introspect the application memory (liveness
checking, non-progression checking, etc), so that we can run the app
in valgrind when we don't need to introspect its memory (safety
checking without non-progression checking).

I know I just moved this chunks of code from ModelChecker to
RemoteProcessMemory to now move it further, and I'm sorry for the
noise, but this code drives me nuts and I need to clean it step by step.