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/editor/src/display_map/block_map.rs

@@ -65,7 +65,7 @@ pub struct CustomBlockId(pub usize);
 
 impl From<CustomBlockId> for ElementId {
     fn from(val: CustomBlockId) -> Self {
-        ElementId::Integer(val.0)
+        val.0.into()
     }
 }