Auto merge of #101708 - compiler-errors:issue-101696, r=jackh726

Normalize closure signature after construction

Astconv can't normalize inputs or outputs with escaping bound vars ([see this](https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_typeck/check/fn_ctxt/mod.rs.html#294)), so normalize them after we've wrapped them in a binder.

Fixes #101696