lualoader: Add primitive hook module, use it to untangle bogus reference

See: comments in the hook module about intended usage, as well as the
introduced use for config.reloaded.

Use the newly introduced hook module to define a "config.reloaded" hook.
This is currently used to register core's clearKernelCache as a reload hook
to avoid a circular dependency and fix this functionality- it didn't
actually work out, and it isn't immediately obvious how it slipped into src.

Other hook types will be introduced into the core lualoader as useful hook
points are identified.