Rollup merge of #84013 - CDirkx:fmt, r=m-ou-se

Replace all `fmt.pad` with `debug_struct`

This replaces any occurrence of:
- `f.pad("X")` with `f.debug_struct("X").finish()`
- `f.pad("X { .. }")` with `f.debug_struct("X").finish_non_exhaustive()`

This is in line with existing formatting code such as
https://github.com/rust-lang/rust/blob/125505306744a0a5bb01d62337260a95d9ff8d57/library/std/src/sync/mpsc/mod.rs#L1470-L1475

diff --cc library/std/src/thread/local.rs
Simple merge