Before this fix, the call to `body()` would crash, since `has_body()`
would return true, but we would try to retrieve the body of an intrinsic
which is not allowed.

Instead, the `Instance::body()` function will now convert an Intrinsic
into an Item before retrieving its body.

`wide_str!` creates a null terminated UTF-16 string whereas `utf16!` just creates a UTF-16 string without adding a null.

This commit does three things:
 1. replaces (the last remaining) never true cfgs by the FALSE cfg
 2. fix derive-helper-configured.rs (typo in directive)
 3. and comment some current unused #[cfg_attr] (missing revisions)

This cuts the HTML overhead for a page by about 1KiB,
significantly reducing the overall size of the docs bundle.

According to <https://caniuse.com/?search=svg%20favicon>,
SVG favicons are supported in everything but Safari.

When I actually try it in Safari, it's downloading all
three favicons, and nothing looks different when I disable
the 16x16 one.

<https://dev.to/masakudamatsu/favicon-nightmare-how-to-maintain-sanity-3al7>,
which is linked from caniuse above, recommends an ico.
However, the reason they recommend it is the apps that
only support /favicon.ico exactly, and rustdoc can't assume
it will be installed to the site root, so it's unfortunately
up to the webmaster to make sure it's set up.

…that theyre coming from the same place

Add `REDUNDANT_LIFETIMES` lint to detect lifetimes which are semantically redundant

There already is a `UNUSED_LIFETIMES` lint which is fired when we detect where clause bounds like `where 'a: 'static`, however, it doesn't use the full power of lexical region resolution to detect failures.

Right now `UNUSED_LIFETIMES` is an `Allow` lint, though presumably we could bump it to warn? I can (somewhat) easily implement a structured suggestion so this can be rustfix'd automatically, since we can just walk through the HIR body, replacing instances of the redundant lifetime.

Fixes rust-lang#118376
r? lcnr

Windows: set main thread name without re-encoding

As a minor optimization, we can skip the runtime UTF-8 to UTF-16 conversion.

…-obk

Add support to intrinsics fallback body

Before this fix, the call to `body()` would crash, since `has_body()` would return true, but we would try to retrieve the body of an intrinsic which is not allowed.

Instead, the `Instance::body()` function will now convert an Intrinsic into an Item before retrieving its body.

Note: I also changed how we monomorphize the instance body. Unfortunately, the call still ICE for some shims.

r? `@oli-obk`

…erics, r=oli-obk

Add const generics support for pattern types

r? `@oli-obk`

…checking, r=WaffleLapkin

Only assert for child/parent projection compatibility AFTER checking that theyre coming from the same place

This assertion doesn't make sense until we check that these captures are actually equivalent.

Fixes rust-lang#123697

<sub>Some days I wonder how I even write code that works...</sub>

…eck-cfg-2, r=jieyouxu

Further cleanup cfgs in the UI test suite

This PR does more cleanup of cfgs in our UI test suite, in preparation for adding automatic always on check-cfg (but is IMO worth landing even without that follow up).

To be more specific this PR:
 - replaces (the last remaining) never true cfgs by the `FALSE` cfg
 - fix `proc-macro/derive-helper-configured.rs` *(typo in directive)*
 - and comment some current unused `#[cfg_attr]` *(missing revisions)*

Follow-up to rust-lang#123577.

…r=GuillaumeGomez

rustdoc: reduce per-page HTML overhead

r? `@GuillaumeGomez`