Conflicts:
	src/libcore/atomic.rs
	src/libcore/finally.rs
	src/test/auxiliary/inherited_stability.rs
	src/test/auxiliary/lint_stability.rs

* `core` - for the core crate
* `hash` - hashing
* `io` - io
* `path` - path
* `alloc` - alloc crate
* `rand` - rand crate
* `collections` - collections crate
* `std_misc` - other parts of std
* `test` - test crate
* `rustc_private` - everything else

closes #21402
cc #15294

This commit aims to stabilize the `TypeId` abstraction by moving it out of the
`intrinsics` module into the `any` module of the standard library. Specifically,

* `TypeId` is now defined at `std::any::TypeId`
* `TypeId::hash` has been removed in favor of an implementation of `Hash`.

This commit also performs a final pass over the `any` module, confirming the
following:

* `Any::get_type_id` remains unstable as *usage* of the `Any` trait will likely
  never require this, and the `Any` trait does not need to be implemented for
  any other types. As a result, this implementation detail can remain unstable
  until associated statics are implemented.
* `Any::downcast_ref` is now stable
* `Any::downcast_mut` is now stable
* `BoxAny` remains unstable. While a direct impl on `Box<Any>` is allowed today
  it does not allow downcasting of trait objects like `Box<Any + Send>` (those
  returned from `Thread::join`). This is covered by #18737.
* `BoxAny::downcast` is now stable.

Fixes #21249
Fixes #11540

The example of the `Index` and `IndexMut` trait contained too much `Foo`.
It now contains a bit more `Bar` to make things clearer which parts are
defining the type of the index.

I searched for times when we were hiding functions with # in the documentation,
and fixed them to not use it unless neccesary.

I also made random improvements whenever I changed something. For example,
I changed Example to Examples, for consistency.

Fixes #13423

* Not all traits are part of the prelude anymore
* We switched from pass-by-reference to pass-by-value for most traits
* Add some explanations around pass-by-value traits in the context of
  generic code and additional implementations for reference types.

Fix tabs

Added missing ty_str cases when generating type descriptions

Reduce code duplication and improve test

This outer attribute doesn't actually apply to anything is seems
to be incorrect in what it is saying.

This takes an opportunity to show yet-another-way of dealing with
Results and matching.

No in-tree users. Ugly interface. Closes #14332.

Change any use of AtomicInt to AtomicIsize and AtomicUint to AtomicUsize

Closes #20893

[breaking-change]

This is only relevant to the code that uses generics such as

    fn magic<T: Shl>(a: T) { a << 10u8; }

Fixes #20288

Add ability to attach custom #[on_unimplemented] error messages for unimplemented traits (fixes #20783)

Both `Extend::extend` and `DoubleEndedIterator::next_back` were intended to be
stable, but they mistakenly didn't have the `#[stable]` tag.

The libstd definitions move to libcore, which causes some minor updates there.

Closes #20711

This adds the int_uint feature to *every* library, whether or not it
needs it.