OpenHarmony native vsync bindings

Low-level bindings to the vertical synchronization API on OpenHarmony. A higher level binding is provided by the ohos-vsync crate.

C API reference: https://gitcode.com/openharmony/docs/blob/master/en/application-dev/reference/apis-arkgraphics2d/capi-nativevsync.md

License

Licensed under the Apache-2.0 license, matching the license of OpenHarmony.