Auto merge of #115694 - clarfonthey:std-hash-private, r=dtolnay

Add `std:#️⃣:{DefaultHasher, RandomState}` exports (needs FCP)

This implements rust-lang/libs-team#267 to move the libstd hasher types to `std::hash` where they belong, instead of `std::collections::hash_map`.

<details><summary>The below no longer applies, but is kept for clarity.</summary>
This is a small refactor for #27242, which moves the definitions of `RandomState` and `DefaultHasher` into `std::hash`, but in a way that won't be noticed in the public API.

I've opened rust-lang/libs-team#267 as a formal ACP to move these directly into the root of `std::hash`, but for now, they're at least separated out from the collections code in a way that will make moving that around easier.

I decided to simply copy the rustdoc for `std::hash` from `core::hash` since I think it would be ideal for the two to diverge longer-term, especially if the ACP is accepted. However, I would be willing to factor them out into a common markdown document if that's preferred.
</details>

compiler/rustc_middle/src/ty/error.rs

@@ -7,8 +7,7 @@ use rustc_hir::def_id::DefId;
 use rustc_span::symbol::Symbol;
 use rustc_target::spec::abi;
 use std::borrow::Cow;
-use std::collections::hash_map::DefaultHasher;
-use std::hash::{Hash, Hasher};
+use std::hash::{DefaultHasher, Hash, Hasher};
 use std::path::PathBuf;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]

compiler/rustc_session/src/config.rs

@@ -3178,9 +3178,8 @@ pub(crate) mod dep_tracking {
     use rustc_target::spec::{
         RelroLevel, SanitizerSet, SplitDebuginfo, StackProtector, TargetTriple, TlsModel,
     };
-    use std::collections::hash_map::DefaultHasher;
     use std::collections::BTreeMap;
-    use std::hash::Hash;
+    use std::hash::{DefaultHasher, Hash};
     use std::num::NonZeroUsize;
     use std::path::PathBuf;
 

compiler/rustc_session/src/options.rs

@@ -19,8 +19,7 @@ use rustc_span::SourceFileHashAlgorithm;
 
 use std::collections::BTreeMap;
 
-use std::collections::hash_map::DefaultHasher;
-use std::hash::Hasher;
+use std::hash::{DefaultHasher, Hasher};
 use std::num::{IntErrorKind, NonZeroUsize};
 use std::path::PathBuf;
 use std::str;

compiler/rustc_target/src/spec/mod.rs

@@ -3503,7 +3503,7 @@ impl TargetTriple {
     /// If this target is a path, a hash of the path is appended to the triple returned
     /// by `triple()`.
     pub fn debug_triple(&self) -> String {
-        use std::collections::hash_map::DefaultHasher;
+        use std::hash::DefaultHasher;
 
         match self {
             TargetTriple::TargetTriple(triple) => triple.to_owned(),