Also remove a number of `stage0` annotations and such

We want librustdoc to pickup the env_logger dependency from
the sysroot. This ensures that the same copy of env_logger is used
for both internal crates (e.g. librustc_driver, libsyntax) and
librustdoc

Closes #46383

This is required because the old version depended on tendril 0.3.1,
which used `repr(packed)` incorrectly - see
https://github.com/kuchiki-rs/kuchiki/pull/38

This commit adds a new target to the compiler: wasm32-unknown-unknown. This
target is a reimagining of what it looks like to generate WebAssembly code from
Rust. Instead of using Emscripten which can bring with it a weighty runtime this
instead is a target which uses only the LLVM backend for WebAssembly and a
"custom linker" for now which will hopefully one day be direct calls to lld.

Notable features of this target include:

* There is zero runtime footprint. The target assumes nothing exists other than
  the wasm32 instruction set.
* There is zero toolchain footprint beyond adding the target. No custom linker
  is needed, rustc contains everything.
* Very small wasm modules can be generated directly from Rust code using this
  target.
* Most of the standard library is stubbed out to return an error, but anything
  related to allocation works (aka `HashMap`, `Vec`, etc).
* Naturally, any `#[no_std]` crate should be 100% compatible with this new
  target.

This target is currently somewhat janky due to how linking works. The "linking"
is currently unconditional whole program LTO (aka LLVM is being used as a
linker). Naturally that means compiling programs is pretty slow! Eventually
though this target should have a linker.

This target is also intended to be quite experimental. I'm hoping that this can
act as a catalyst for further experimentation in Rust with WebAssembly. Breaking
changes are very likely to land to this target, so it's not recommended to rely
on it in any critical capacity yet. We'll let you know when it's "production
ready".

---

Currently testing-wise this target is looking pretty good but isn't complete.
I've got almost the entire `run-pass` test suite working with this target (lots
of tests ignored, but many passing as well). The `core` test suite is still
getting LLVM bugs fixed to get that working and will take some time. Relatively
simple programs all seem to work though!

---

It's worth nothing that you may not immediately see the "smallest possible wasm
module" for the input you feed to rustc. For various reasons it's very difficult
to get rid of the final "bloat" in vanilla rustc (again, a real linker should
fix all this). For now what you'll have to do is:

    cargo install --git https://github.com/alexcrichton/wasm-gc
    wasm-gc foo.wasm bar.wasm

And then `bar.wasm` should be the smallest we can get it!

---

In any case for now I'd love feedback on this, particularly on the various
integration points if you've got better ideas of how to approach them!

Signed-off-by: NMarc-Antoine Perennou <Marc-Antoine@Perennou.com>

This commit removes the `rand` crate from the standard library facade as
well as the `__rand` module in the standard library. Neither of these
were used in any meaningful way in the standard library itself. The only
need for randomness in libstd is to initialize the thread-local keys of
a `HashMap`, and that unconditionally used `OsRng` defined in the
standard library anyway.

The cruft of the `rand` crate and the extra `rand` support in the
standard library makes libstd slightly more difficult to port to new
platforms, namely WebAssembly which doesn't have any randomness at all
(without interfacing with JS). The purpose of this commit is to clarify
and streamline randomness in libstd, focusing on how it's only required
in one location, hashmap seeds.

Note that the `rand` crate out of tree has almost always been a drop-in
replacement for the `rand` crate in-tree, so any usage (accidental or
purposeful) of the crate in-tree should switch to the `rand` crate on
crates.io. This then also has the further benefit of avoiding
duplication (mostly) between the two crates!

This affects regular code generation as well as constant evaluation in trans,
but not the HIR constant evaluator because that one returns an error for
overflowing casts and NaN-to-int casts. That error is conservatively
correct and we should be careful to not accept more code in constant
expressions.
The changes to code generation are guarded by a new -Z flag, to be able
to evaluate the performance impact. The trans constant evaluation changes
are unconditional because they have no run time impact and don't affect
type checking either.

These tools have been corrected in their upstream repo's, and the
submodules have been updated here to reflect that. I also had to update
Cargo to match what the RLS is expecting.

The tool states for `rustfmt` and `rls` where both changed from "Broken"
to "Testing" in this commit, thus enabling testing and distribution
again.

This is intended to prevent the spurious OOM error from
run-pass/rustc-rust-log.rs, by skipping the output in the middle when the
size is over 416 KB, so that the log output will not be overwhelmed.

This allows rustfmt and the RLS to test and compile again.

This commit updates the bootstrap compiler, bumps the version to 1.23, updates
Cargo, updates books, and updates crates.io dependencies

This reverts commit 6484258f.

fixes #45420

This reverts commit a49157dc30bf7a163200b10d63a71b005a1376e3.

This updates the borrowck query to return a result, and this result is then used
to incrementally check for unused mutable nodes given sets of all the used
mutable nodes.

Closes #42384