To detect instruction aborts, a helper to Registers.h is added, and used
in Interrupts.cpp. Additionally, the PageFault class gets a setter to
set the PageFaults m_is_instruction_fetch bool, and is also used in
Interrupts.cpp.
The class used to look at the x86_64 specific exception code to figure
out what kind of page fault happend, however this refactor allows
aarch64 to use the same class.