Rollup merge of #146250 - fmease:bump-stage0-rustfmt, r=Mark-Simulacrum

Bump stage0 rustfmt

Unblocks #146071, cc `@npmccallum.`

Steps to reproduce:

1. Temporarily upgrade `src/tools/bump-stage0`'s `toml` dependency from 0.7 to 0.9 to fix build error (see Zulip topic)
2. Execute `./x run src/tools/bump-stage0`
3. Manually revert changes unrelated to nightly `rustfmt`+`rustc` (the latter needs to be bumped, too, for the driver ([via](#146250 (comment))))

r? `@Mark-Simulacrum` as discussed in [#t-release > Bump stage0 rustfmt separately ("one-off")](https://rust-lang.zulipchat.com/#narrow/channel/241545-t-release/topic/Bump.20stage0.20rustfmt.20separately.20.28.22one-off.22.29/with/537916615)

Author: fmease