arch-arm: Implementation of SelfHosted Debug Software step

arch-arm: Implementation of SelfHosted Debug Software step

This commit implements SelfHosted Debug Software step as is defined in
Armv8 Reference manual chapter D2.

+ decoder.hh/cc/isa: Checks the software step bit in order to skip the instruction
              before its decode.
+ faults.hh/cc: implemented SoftwareStep exception and proper modification
                of spsr during the invoke of other exceptions
+ isa.cc: Set debug mask if needed during cpsr modification
+ tlb.cc: Checks if software step is in ACTIVE state to avoid trigger
          breakpoint or watchpoint exception
+ self_debug.hh/cc: Implementation of State change and ss bit based during eret.
+ types.hh: Define sofware step flags like step, load or stepped to check the different flags
        that triggering software step should use for the ISS code.
+ pseudo.hh/isa: Triggers the sofware step esception after decode.
+ static_inst.cc: Call debugExceptionReturnsSS durint eret routine.

Change-Id: I3a64507c64842c34c76ad7f6daa5f4306bd55d2c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30617
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>