[rtl] Fix hardware breakpoints and exceptions interaction
[rtl] Fix hardware breakpoints and exceptions interaction

This change will cause the ID stage to stall if there is a potential
debug mode entry until instructions in both ID and WB have completed.
This fixes an issue with incorrect behaviour around hardware breakpoints
and exceptions that could cause exception entry to be missed, hardware
breakpoints to be triggered incorrectly or missed entirely.

In addition single step control logic is altered to work correctly with
the new debug mode entry behaviour.

AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex