Previous version does not show that or_insert does not insert the
passed value, as the passed value was the same value as what was
already in the map.

Rollup of 17 pull requests

Successful merges:

 - #55182 (Redox: Update to new changes)
 - #55211 (Add BufWriter::buffer method)
 - #55507 (Add link to std::mem::size_of to size_of intrinsic documentation)
 - #55530 (Speed up String::from_utf16)
 - #55556 (Use `Mmap` to open the rmeta file.)
 - #55622 (NetBSD: link libstd with librt in addition to libpthread)
 - #55750 (Make `NodeId` and `HirLocalId` `newtype_index`)
 - #55778 (Wrap some query results in `Lrc`.)
 - #55781 (More precise spans for temps and their drops)
 - #55785 (Add mem::forget_unsized() for forgetting unsized values)
 - #55852 (Rewrite `...` as `..=` as a `MachineApplicable` 2018 idiom lint)
 - #55865 (Unix RwLock: avoid racy access to write_locked)
 - #55901 (fix various typos in doc comments)
 - #55926 (Change sidebar selector to fix compatibility with docs.rs)
 - #55930 (A handful of hir tweaks)
 - #55932 (core/char: Speed up `to_digit()` for `radix <= 10`)
 - #55956 (add tests for some fixed ICEs)

Failed merges:

r? @ghost

Clarifying documentation for collections::hash_map::Entry::or_insert

Previous version does not show that or_insert does not insert the passed value, as the passed value was the same value as what was already in the map.

It used to point to the implementation PR.

Fix bug in from_key_hashed_nocheck

…hat) on asymmetrically sized sets and extend unit tests slightly beyond that

Previously "with a custom type as key", now "with a custom key type"

Fixed typo in HashMap documentation

Previously "with a custom type as key", now "with a custom key type"

Add example of using the indexing operator to HashMap docs

Fixes #52575

Found with `git grep -P '\b([a-z]+)\s+\1\b'`

Notably, hash iterators don't require any trait bounds to be iterated.

There are two big categories of changes in here

- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop` & `Debug`)
- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)

I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations where the flipped one cannot elide the lifetime.

Use more impl header lifetime elision

Inspired by seeing explicit lifetimes on these two:

- https://doc.rust-lang.org/nightly/std/slice/struct.Iter.html#impl-FusedIterator
- https://doc.rust-lang.org/nightly/std/primitive.u32.html#impl-Not

And a follow-up to rust-lang/rust#54687, that started using IHLE in libcore.

Most of the changes in here fall into two big categories:

- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop`, `Debug`, and `Clone`)

- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)

I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations [where the flipped one cannot elide the lifetime](https://internals.rust-lang.org/t/impl-type-parameter-aliases/9403/2?u=scottmcm).

I also removed two lifetimes that turned out to be completely unused; see rust-lang/rust#41960 (comment)

Relax some Hash bounds on HashMap<K, V, S> and HashSet<T, S>

Notably, hash iterators don't require any trait bounds to be iterated.

Make the Entry API of HashMap<K, V> Sync and Send

Fixes #45219

A few improvements to comments in user-facing crates

Not too many this time, and all concern comments (almost all doc comments) in user-facing crates (libstd, libcore, liballoc).

r? @steveklabnik

Merged as of rust commit e938c2b9aae7, just before hashbrown.