Migrate from winapi to windows-sys (#4346)

* Migrate from `winapi` to `windows-sys`

I believe that Microsoft itself is supporting the development of
`windows-sys` and it's also used by `cap-std` now so this switches
Wasmtime's dependencies on Windows APIs from the `winapi` crate to the
`windows-sys` crate. We still have `winapi` in our dependency graph but
that may get phased out over time.

* Make windows-sys a target-specific dependency

crates/cache/src/worker.rs

@@ -230,8 +230,7 @@ impl WorkerThread {
 
     #[cfg(target_os = "windows")]
     fn lower_thread_priority() {
-        use winapi::um::processthreadsapi::{GetCurrentThread, SetThreadPriority};
-        use winapi::um::winbase::THREAD_MODE_BACKGROUND_BEGIN;
+        use windows_sys::Win32::System::Threading::*;
 
         // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-setthreadpriority
         // https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities