chore: remove platform FingerId

The same as for `WindowId`.

src/event.rs

@@ -634,12 +634,23 @@ impl DeviceId {
 /// Whenever a touch event is received it contains a `FingerId` which uniquely identifies the finger
 /// used for the current interaction.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct FingerId(pub(crate) platform_impl::FingerId);
+pub struct FingerId(pub(crate) usize);
 
 impl FingerId {
-    #[cfg(test)]
-    pub(crate) const fn dummy() -> Self {
-        FingerId(platform_impl::FingerId::dummy())
+    /// Convert the [`FingerId`] into the underlying integer.
+    ///
+    /// This is useful if you need to pass the ID across an FFI boundary, or store it in an atomic.
+    #[allow(dead_code)]
+    pub(crate) const fn into_raw(self) -> usize {
+        self.0
+    }
+
+    /// Construct a [`FingerId`] from the underlying integer.
+    ///
+    /// This should only be called with integers returned from [`FingerId::into_raw`].
+    #[allow(dead_code)]
+    pub(crate) const fn from_raw(id: usize) -> Self {
+        Self(id)
     }
 }
 
@@ -1154,7 +1165,7 @@ mod tests {
         ($closure:expr) => {{
             #[allow(unused_mut)]
             let mut x = $closure;
-            let fid = event::FingerId::dummy();
+            let fid = event::FingerId::from_raw(0);
 
             #[allow(deprecated)]
             {
@@ -1291,7 +1302,7 @@ mod tests {
         });
         let _ = event::StartCause::Init.clone();
 
-        let fid = crate::event::FingerId::dummy().clone();
+        let fid = crate::event::FingerId::from_raw(0).clone();
         HashSet::new().insert(fid);
         let mut set = [fid, fid, fid];
         set.sort_unstable();