CVA6-DV : Update cva6-dv to support cvxif custom instruction base on new spec

Created by: AyoubJalali

Hello, This PR related to CVA6-DV to generate custom instruction for the cvxif agent, also I add more exception handler for more exception like LOAD/STORE/INST_ADD_MISALIGNED (Embedded cores does not have this problem), also I add a file cva6_signature to add more exception, just to generate a proper test to handle any exception raise by the CUS_EXC instruction.