chore(util/lua): remove dead code

I removed lua_module helper class because it does not work.
The problem is that the linker may eliminate ignore a object file that contains a lua_module global object used for initialization. When this happens, the associated Lua bindings will not be exposed in the Lua API.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
chore(util/lua): remove dead code