Export surface::Surface as Surface

In frameworks/native/aidl/gui/android/view/Surface.aidl, the rust type
for the parcelable Surface is `nativewindow::Surface`. To match with
that, crate::surface::Surface has to be exported as Surface.

If without this change, an AIDL rust backend using Surface experiences
the following error.

error[E0412]: cannot find type `Surface` in crate `nativewindow`
   --> out/soong/.intermediates/packages/modules/Virtualization/libs/android_display_backend/libcrosvm_android_display_service-rust/android_arm64_armv8-a_source/libcrosvm_android_display_service.rs:141:77
    |
141 |           fn r#setSurface<'a>(&'a self, _arg_surface: &'a mut nativewindow::Surface) -> binder::BoxFuture<'a, binder::Result<()>> {
    |                                                                             ^^^^^^^ not found in `nativewindow`
    |
help: consider importing this struct
    |
17  +         use nativewindow::surface::Surface;
    |
help: if you import `Surface`, refer to it directly
    |
141 -           fn r#setSurface<'a>(&'a self, _arg_surface: &'a mut nativewindow::Surface) -> binder::BoxFuture<'a, binder::Result<()>> {
141 +           fn r#setSurface<'a>(&'a self, _arg_surface: &'a mut Surface) -> binder::BoxFuture<'a, binder::Result<()>> {

Bug: N/A
Test: m
Change-Id: I20f13fd378890b803ce53ce654ee74a610f1a1c8