Add `std::hash::{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 rust-lang#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>

see https://github.com/rust-lang/rust/releases/tag/1.76.0
see rust-lang/rust#115694

see https://github.com/rust-lang/rust/releases/tag/1.76.0
see rust-lang/rust#115694

…d::hash`

see https://github.com/rust-lang/rust/releases/tag/1.76.0
see rust-lang/rust#115694

* chore(src/lib.rs): `RandomState` now exported in `std::hash`

see https://github.com/rust-lang/rust/releases/tag/1.76.0
see rust-lang/rust#115694

* chore(ci/cd): handle `rustup update stable`

when there is a version mismatch between stable toolchain
installed on runner (used) and stable toolchain available
from upstream (latest)

* chore(src/lib.rs): `{RandomState, DefaultHasher}` now exported in `std::hash`

see https://github.com/rust-lang/rust/releases/tag/1.76.0
see rust-lang/rust#115694

* chore(ci): handle `rustup update stable`

when there is a version mismatch between stable toolchain
installed on runner (used) and stable toolchain available
from upstream (latest)

Pkgsrc changes:
 * Adapt checksums and patches.

Upstream chnages:

Version 1.76.0 (2024-02-08)
==========================

Language
--------
- [Document Rust ABI compatibility between various types]
  (rust-lang/rust#115476)
- [Also: guarantee that char and u32 are ABI-compatible]
  (rust-lang/rust#118032)
- [Warn against ambiguous wide pointer comparisons]
  (rust-lang/rust#117758)

Compiler
--------
- [Lint pinned `#[must_use]` pointers (in particular, `Box<T>`
  where `T` is `#[must_use]`) in `unused_must_use`.]
  (rust-lang/rust#118054)
- [Soundness fix: fix computing the offset of an unsized field in
  a packed struct]
  (rust-lang/rust#118540)
- [Soundness fix: fix dynamic size/align computation logic for
  packed types with dyn Trait tail]
  (rust-lang/rust#118538)
- [Add `$message_type` field to distinguish json diagnostic outputs]
  (rust-lang/rust#115691)
- [Enable Rust to use the EHCont security feature of Windows]
  (rust-lang/rust#118013)
- [Add tier 3 {x86_64,i686}-win7-windows-msvc targets]
  (rust-lang/rust#118150)
- [Add tier 3 aarch64-apple-watchos target]
  (rust-lang/rust#119074)
- [Add tier 3 arm64e-apple-ios & arm64e-apple-darwin targets]
  (rust-lang/rust#115526)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------
- [Add a column number to `dbg!()`]
  (rust-lang/rust#114962)
- [Add `std::hash::{DefaultHasher, RandomState}` exports]
  (rust-lang/rust#115694)
- [Fix rounding issue with exponents in fmt]
  (rust-lang/rust#116301)
- [Add T: ?Sized to `RwLockReadGuard` and `RwLockWriteGuard`'s Debug impls.]
  (rust-lang/rust#117138)
- [Windows: Allow `File::create` to work on hidden files]
  (rust-lang/rust#116438)

Stabilized APIs
---------------
- [`Arc::unwrap_or_clone`]
  (https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.unwrap_or_clone)
- [`Rc::unwrap_or_clone`]
  (https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.unwrap_or_clone)
- [`Result::inspect`]
  (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.inspect)
- [`Result::inspect_err`]
  (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.inspect_err)
- [`Option::inspect`]
  (https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.inspect)
- [`type_name_of_val`]
  (https://doc.rust-lang.org/stable/std/any/fn.type_name_of_val.html)
- [`std::hash::{DefaultHasher, RandomState}`]
  (https://doc.rust-lang.org/stable/std/hash/index.html#structs)
  These were previously available only through `std::collections::hash_map`.
- [`ptr::{from_ref, from_mut}`]
  (https://doc.rust-lang.org/stable/std/ptr/fn.from_ref.html)
- [`ptr::addr_eq`](https://doc.rust-lang.org/stable/std/ptr/fn.addr_eq.html)

Cargo
-----

See [Cargo release notes]
(https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-176-2024-02-08).

Rustdoc
-------
- [Don't merge cfg and doc(cfg) attributes for re-exports]
  (rust-lang/rust#113091)
- [rustdoc: allow resizing the sidebar / hiding the top bar]
  (rust-lang/rust#115660)
- [rustdoc-search: add support for traits and associated types]
  (rust-lang/rust#116085)
- [rustdoc: Add highlighting for comments in items declaration]
  (rust-lang/rust#117869)

Compatibility Notes
-------------------
- [Add allow-by-default lint for unit bindings]
  (rust-lang/rust#112380)
  This is expected to be upgraded to a warning by default in a future Rust
  release. Some macros emit bindings with type `()` with user-provided spans,
  which means that this lint will warn for user code.
- [Remove x86_64-sun-solaris target.]
  (rust-lang/rust#118091)
- [Remove asmjs-unknown-emscripten target]
  (rust-lang/rust#117338)
- [Report errors in jobserver inherited through environment variables]
  (rust-lang/rust#113730)
  This [may warn](rust-lang/rust#120515)
  on benign problems too.
- [Update the minimum external LLVM to 16.]
  (rust-lang/rust#117947)
- [Improve `print_tts`](rust-lang/rust#114571)
  This change can break some naive manual parsing of token trees
  in proc macro code which expect a particular structure after
  `.to_string()`, rather than just arbitrary Rust code.
- [Make `IMPLIED_BOUNDS_ENTAILMENT` into a hard error from a lint]
  (rust-lang/rust#117984)
- [Vec's allocation behavior was changed when collecting some iterators]
  (rust-lang/rust#110353)
  Allocation behavior is currently not specified, nevertheless
  changes can be surprising.
  See [`impl FromIterator for Vec`]
  (https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#impl-FromIterator%3CT%3E-for-Vec%3CT%3E)
  for more details.
- [Properly reject `default` on free const items]
  (rust-lang/rust#117818)