Use u64 instead of usize in ElementId (#29493)

Truncation to a 32 bit `usize` could cause two distinct IDs to be
considered the same element.

Release Notes:

- N/A

crates/markdown/src/markdown.rs

@@ -1167,7 +1167,7 @@ fn render_copy_code_block_button(
     markdown: Entity<Markdown>,
     cx: &App,
 ) -> impl IntoElement {
-    let id = ElementId::NamedInteger("copy-markdown-code".into(), id);
+    let id = ElementId::named_usize("copy-markdown-code", id);
     let was_copied = markdown.read(cx).copied_code_blocks.contains(&id);
     IconButton::new(
         id.clone(),