WAW hazards elimination

This PR introduces a new RAW hazard detection mechanism to eliminate WAW hazards in CVA6 issue stage.

It first checks for hazards in all scoreboard entries in parallel. Then it filters found hazards before vs after the current issue pointer. It then finds the index of the last hazard before (resp. after) the issue pointer. Finally, it gives precedence to a hazard before the issue pointer over the one after the issue pointer.