Use multiple threads to concurrently run multiple FI experiments

[uditagarwal97]

Currently, LLTFI runs FI experiments sequentially, which makes the FI significantly slow.
Moving forward, we can parallelize the FI engine of LLTFI so as to exploit multi-cores for concurrently running FI experiments.

This change will require us to use an alternate mechanism for passing the FI parameters after the profiling phase to the runtime fault injection part. Currently, these parameters are passed using a fixed file. (llfi.stat.[something]).

[uditagarwal97]

I tried to parallelize LLTFI's fault injection, but it looks like that it's going to take a significant rework of the runtime fault injection library and injectfault.py script. Therefore, I'm marking this issue as a "major change required" and closing it for now.