Adapt to clippy API changes.

[hkratz]

Against the rustup branch.

Part of the fix for rust-lang/rust#91543

[flip1995]

Those changes are already included in RLS master, but not synced to the Rust repo, because for that, Racer would have to be fixed first. See #1753

[hkratz]

Ah, thanks!

Is the Racer fix really needed immediately if a dummy thread_local_const_init feature gate is reintroduced? That will make rustc-ap-rustc_span build again.

[flip1995]

I think the thread_local_const_init fixes the feature gate thing. But I'm not sure if the Clippy issue can be fixed without a sync. (But let's figure this out in the Zulip thread)