Rollup merge of #126354 - compiler-errors:variance, r=lcnr

Use `Variance` glob imported variants everywhere

Fully commit to using the globbed variance. Could be convinced the other way, and change this PR to not use the globbed variants anywhere, but I'd rather we do one or the other.

r? lcnr

compiler/rustc_middle/src/ty/mod.rs

@@ -16,7 +16,6 @@ pub use self::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeV
 pub use self::AssocItemContainer::*;
 pub use self::BorrowKind::*;
 pub use self::IntVarValue::*;
-pub use self::Variance::*;
 use crate::error::{OpaqueHiddenTypeMismatch, TypeMismatchReason};
 use crate::metadata::ModChild;
 use crate::middle::privacy::EffectiveVisibilities;