Change SetInterface and GetInterface to standard Go functions,
removing direct NAPI handling and async logic from wgctrl.go.
Use napi.GoFuncOf for function registration in addon.go.
Update napi-go dependency to v0.1.2 pre-release.
Replace the old `addon` package with `wg_addon` and switch the N-API
binding library from `abhisekp/napi-go` to
`Sirherobrine23/napi-go`.
This restructures the code to use `wgctrl` for Linux/Windows in
`wg_addon/wgctrl.go` and stubs a `wireguard-go` based implementation
for other Unix systems in `wg_addon/unix.go`. N-API registration and
common types are now in `wg_addon/addon.go`.
The implementation leverages features of the new N-API library, such as
struct tags for automatic marshalling and simplified async worker
creation.
