`Ok(0)` is indeed something the caller may interpret as an error, but
that's the *correct* thing to return if the writer can't accept any more
bytes.

this version is the one containing the workaround for the provider API
changes on nightly

Unstable Book: update `lang_items` page and split it

[`lang_items` rendered](https://github.com/kadiwa4/rust/blob/lang_items_doc/src/doc/unstable-book/src/language-features/lang-items.md), [`start` rendered](https://github.com/kadiwa4/rust/blob/lang_items_doc/src/doc/unstable-book/src/language-features/start.md)
Closes rust-lang#110274
Rustonomicon PR: rust-lang/nomicon#413, Rust Book PR: rust-lang/book#3705

A lot of information doesn't belong on the `lang_items` page. I added a separate page for the `start` feature and moved some text into the Rustonomicon because the `lang_items` page should not be a tutorial on how to build a `#![no_std]` executable.
The list of existing lang items is too long/unstable, so I removed it.

The doctests still don't work. :(

…r=m-ou-se

Partially revert rust-lang#107200

`Ok(0)` is indeed something the caller may interpret as an error, but
that's the *correct* thing to return if the writer can't accept any more
bytes.

…vidtwco

Fix suggestion for attempting to define a string with single quotes

Currently attempting to compile `fn main() { let _ = '\\"'; }` will result in the following error message:
```
error: character literal may only contain one codepoint
 --> src/main.rs:1:21
  |
1 | fn main() { let _ = '\\"'; }
  |                     ^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | fn main() { let _ = "\\""; }
  |                     ~~~~~
```
The suggestion is invalid as it fails to escape the `"`. This PR fixes the suggestion so that it now reads:
```
help: if you meant to write a `str` literal, use double quotes
  |
1 | fn main() { let _ = "\\\""; }
  |                     ~~~~~~
```
The relevant test is also updated to ensure that this does not regress in future.

…rors

Revert PR rust-lang#114052 to fix invalid suggestion

This PR reverts rust-lang#114052 to fix the invalid suggestion produced by the PR.

Unfortunately the invalid suggestion cannot be improved from the current position where it's emitted since we lack enough information (is an assignment?, left or right?, ...) to be able to fix it here. Furthermore the previous wasn't wrong, just suboptimal, contrary to the current one which is just wrong.

Added a regression test and commented out some code instead of removing it so we can use it later.

Reopens rust-lang#114050
Fixes rust-lang#114925

update `thiserror` to version >= 1.0.46

1.0.46 version is the one with [the workaround](dtolnay/thiserror#248) for rust-lang#114839. I'm also encountering this issue, so let's update the dependency so that everyone doesn't have to `./x clean`.

Fixes rust-lang#114839.

r? `@RalfJung`