Rollup merge of #128135 - joboet:reduplicate_tls, r=tgross35

std: use duplicate thread local state in tests

With rust-lang/miri#3739 merged, the deduplication hack is no longer necessary.

library/std/src/thread/mod.rs

@@ -192,12 +192,6 @@ pub use scoped::{scope, Scope, ScopedJoinHandle};
 #[macro_use]
 mod local;
 
-cfg_if::cfg_if! {
-    if #[cfg(test)] {
-        // Avoid duplicating the global state associated with thread-locals between this crate and
-        // realstd. Miri relies on this.
-        pub use realstd::thread::{local_impl, AccessError, LocalKey};
-    } else {
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::local::{AccessError, LocalKey};
 
@@ -207,8 +201,6 @@ cfg_if::cfg_if! {
 pub mod local_impl {
     pub use crate::sys::thread_local::*;
 }
-    }
-}
 
 ////////////////////////////////////////////////////////////////////////////////
 // Builder