feat: introduce SError exception handler

Introduce SError exception handler along with support to register a
custom handler. The default behaviour is same as before if no handler
is registered.
This patch will allow tests to do a graceful exit after handling an
SError.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Idbe37d3690e3a8e08fa3b0dff496d18d3022a8fc
4 files changed