Ask lager and immer to always use exceptions

Summary:
lager and immer now have a definition for it to always enable exceptions support. When it is well-supported we can drop the `#include <libkazv-config.hpp>` line.

Type: skip

Test Plan: Verify unit tests pass.

Reviewers: O1 the Kazv Project

Differential Revision: https://iron.lily-is.land/D185