Rollup merge of #124168 - oli-obk:define_opaque_types12, r=lcnr

Use `DefiningOpaqueTypes::Yes` in rustdoc, where the `InferCtxt` is guaranteed to have no opaque types it can define

r? `@lcnr`

I manually checked there it's always `tcx.infer_ctxt().build()`

Author: matthiaskrgr