As discussed in rust-lang#88576, raw handle values in Windows can be null, such
as in `windows_subsystem` mode, or when consoles are detached from a
process. So, don't use `NonNull` to hold them, don't assert that they're
not null, and remove `OwnedHandle`'s `repr(transparent)`. Introduce a
new `HandleOrNull` type, similar to `HandleOrInvalid`, to cover the FFI
use case.

(cherry picked from commit 3b97481)

(cherry picked from commit e102c2a)

(cherry picked from commit 5d79870)

Fixes: rust-lang#89658
(cherry picked from commit 1bb399c)

This lint is not yet ready for stable use, primarily due to false positives in edge
cases; we want to test it out more before stabilizing.

(cherry picked from commit 185fa56)

In rust-lang#89522 we learned that `clone3` is interacting poorly with Gentoo's
`sandbox` tool. We only need that for the unstable pidfd extensions, so
otherwise avoid that and use a normal `fork`.

(cherry picked from commit 85b55ce)

(cherry picked from commit fa2eee7)

Co-authored-by: Josh Triplett <josh@joshtriplett.org>
(cherry picked from commit 6edaaa6)

This reverts commit 12fbabd.

It was only needed because of using raw `clone3` instead of `fork`, but
we only do that now when a pidfd is requested.

(cherry picked from commit e96a0a8)

And add a rustdoc-gui test confirming various header sizes.

(cherry picked from commit 89276ff)

See rust-lang#90024 (comment)

(cherry picked from commit 9158fc2)

Uses 2 MCVEs from the issue tracker that test opposite sides of the problem.

(cherry picked from commit eae42fd)

(cherry picked from commit aff37f8)

(cherry picked from commit 4b97023)

(cherry picked from commit c6b6901)

(cherry picked from commit 0199a81)

(cherry picked from commit 6771ac3)

This helps with (but does not fix)
rust-lang#84738. I tested on
jyn514/objr@edcee7b
and still hit ICEs.

(cherry picked from commit cdafe99)

This *continues* to cause regressions. This code will be unnecessary
once access to the resolver happens fully before creating the tyctxt
(rust-lang#83761), so load all crates unconditionally for now.

(cherry picked from commit 51345a8)

(cherry picked from commit d50a475)

(cherry picked from commit d7afbf6)

The adjustments are used later by ExprUseVisitor to build Place projections
and without adjustments it can produce invalid result.

(cherry picked from commit f556075)

(cherry picked from commit 9c84ac8)

(cherry picked from commit 76bc027)

(cherry picked from commit fc8113d)

(cherry picked from commit 4154e8a)

(cherry picked from commit 9db9811)

(cherry picked from commit 3a687e7)

(cherry picked from commit aef51a0)

(cherry picked from commit a24e2ed)

(cherry picked from commit 530cd5b)