fix(userspace): handle exceptions for process_k8s_audit_event

This fix has two major points in it:

- when `std::stoll` is used in parse_as_int64 handle all the exceptions it
can throw (https://en.cppreference.com/w/cpp/string/basic_string/stol)
- when `process_k8s_audit_event` an eventual exception in it does not
stop the webserver process. This is done by doing a catch all handle
outside it and by logging an error message to the caller as well as in
stderr

Signed-off-by: Lorenzo Fontana <lo@linux.com>

userspace/engine/json_evt.cpp

@@ -281,7 +281,11 @@ bool json_event_value::parse_as_int64(int64_t &intval, const std::string &val)
 			return false;
 		}
 	}
-	catch (std::invalid_argument &e)
+	catch(std::out_of_range &)
+	{
+		return false;
+	}
+	catch (std::invalid_argument &)
 	{
 		return false;
 	}