`rustfmt` no longer builds after rust-lang/rust#78334

[rust-highfive]

Hello, this is your friendly neighborhood mergebot.
After merging PR #78334, I observed that the tool rustfmt no longer builds.
A follow-up PR to the repository https://github.com/rust-lang/rustfmt is needed to fix the fallout.

cc @jonas-schievink, do you think you would have time to do the follow-up work?
If so, that would be great!

[calebcartwright]

We'll need a new rustc-ap version that contains the rustc_data_structures updates from #76614

At a minimum the steps will include:

• (1) get new versions of rustc-ap crates published (will be v686), next scheduled run is Tuesday morning, 27th of October
• (2) bump rustc-ap* in racer and publish new version on crates.io (Bump rustc ap racer-rust/racer#1140)
• (2) bump rustc-ap* on rustfmt 1.4.24 branch and publish new version on crates.io (prepare v1.4.24 release rustfmt#4514)
• (3) update racer and rustfmt references in rls (bump rustfmt to v1.4.24 rls#1705)
• (4) update rustfmt and rls submods in rust-lang/rust repo (Bump Rustfmt and RLS #78775)

Note that the rustc-ap bumps in racer and rustfmt can be done in parallel (step 2's), the other tasks all have to be sequenced

Edit - had to restart a few steps due to subsequent changes merged in rustc

[ghedo]

Racer PR racer-rust/racer#1140
rustfmt PR rust-lang/rustfmt#4495

[ghedo]

I just realized that we also need the rusfmt fix for the 1.4.23 branch as well, so I made rust-lang/rustfmt#4501 for that.

[calebcartwright]

Blocked on #78549 for the time being

[Aaron1011]

#78549 has now been fixed