Rollup merge of #91404 - nnethercote:fix-bad-NodeId-limit-checking, r=dtolnay

Fix bad `NodeId` limit checking.

`Resolver::next_node_id` converts a `u32` to a `usize` (which is
possibly bigger), does a checked add, and then converts the result back
to a `u32`. The `usize` conversion completely subverts the checked add!

This commit removes the conversion to/from `usize`.