Rollup merge of #66850 - eddyb:span-free-formats, r=oli-obk

rustc: hide HirId's fmt::Debug output from -Z span_free_formats.

This replaces the only occurrences of `HirId {...}` from tests with paths, i.e.:
```rust
[closure@HirId { owner: DefIndex(4), local_id: 15 } q:&i32, t:&T]
```
becomes, after this PR:
```rust
[closure@foo<T>::{{closure}}#0 q:&i32, t:&T]
```

r? @oli-obk cc @michaelwoerister

diff --cc src/librustc/mir/mod.rs
Simple merge

diff --cc src/librustc/ty/print/pretty.rs
Simple merge