Integrate Android into ABI

[keeshux]

First, logging. Repurpose NSLogDestination as platform-oriented SimpleLogDestination:

• NSLog on Apple
• Logcat on Android
• printf() elsewhere, with stderr for errors

Then, rather than exposing complex C functions in the ABI, only receive an optional subject for the tunctrl.h signatures (the ref argument):

• pp_tun_ctrl_set_tunnel
• pp_tun_ctrl_configure_sockets
• pp_tun_ctrl_clear_tunnel

If present, VirtualTunnelController will forward the ref to all the tunctrl.h callbacks in the similarly named methods of TunnelController:

• setTunnelSettings → pp_tun_ctrl_set_tunnel(ref, ...)
• configureSockets → pp_tun_ctrl_configure_sockets(ref, ...)
• clearTunnelSettings → pp_tun_ctrl_clear_tunnel(ref, ...)

Therefore, VirtualTunnelControllerImpl is no longer needed.

The Android basic tun controller is paired with the Kotlin code in PartoutVpnWrapper, which tunctrl.c invokes via JNI. Later, VirtualTunnelController will need to encode the TunnelRemoteInfo parameter as JSON so that Kotlin can decode and apply the modules with VpnService.Builder. Linux/Windows will likely be pure C.

Finally, simplify the way wg-go is linked because there's no need to use dlopen() / LoadLibrary(). However, cgo doesn't generate an import lib on Windows, so this must be done POSTBUILD with gendef/dlltool.