FI capabilities in core

[enthusiastic-enthusiast]

1. Add fault_injection model in a new directory which corresponds to Fault Injection Controller (FIC). One C++ file and one Python file. Aimed to be rather self-contained.
2. For targeted components, add modifications to enable fault injection. Usual pattern: targeted component registers with FIC from reset() and provides all necessary information to FIC to allow for fault injection. The associated Python wrapper files are adjusted accordingly to allow for fault injection option. Somewhat more changes to memory.cpp due to stuck-at faults which require holding auxiliary state.
   2.1. Adjust cache_impl.cpp to allow for fault injection into I$ and L0s.
   2.2. Adjust prefetch_single_line.{cpp,hpp} for fault injection into prefetcher buffer.
   2.3. Allow for VREG FI by adjusting vector.{cpp,hpp}
   2.4. Changes to memory.cpp. In particular model stuck-at faults by enforcing fault at associated memory writes.
   2.5. Changes to associated Python wrapper files to allow for fault injection option.