Implement CLIC spec chapter 8.4 - Exception handling

Created by: silabs-oysteink

The spec states:

"Horizontal synchronous exception traps, which stay within a privilege mode, are serviced with the same interrupt level as the instruction that raised the exception. Vertical synchronous exception traps, which are serviced at a higher privilege mode, are taken at interrupt level 0 in the higher privilege mode."

This is not yet currently implemented.