Also stabilizes saturating_int_assign_impl, rust-langgh-92354.

And also make pub fns const where the underlying saturating_*
fns became const in the meantime since the Saturating type was
created.

Remove Drop impl of mpsc Receiver and (Sync)Sender

This change removes the empty `Drop` implementations for `mpsc::Receiver`, `mpsc::Sender` and `mpsc::SyncSender`. These implementations do not specify `#[may_dangle]`, so by removing them we make `mpsc` types play nice with drop check.

This was previously attempted in [rust-lang#105243](rust-lang#105243 (comment)) but then [abandoned due to a test failure](rust-lang#105243 (comment)). I've aligned the test with those for `Mutex` and `RwLock`.

…olnay

make `Debug` impl for `ascii::Char` match that of `char`

# Objective
use a more recognisable format for the `Debug` impl on `ascii::Char` than the derived one based off the enum variants. The alogorithm used is the following:
 - escape `ascii::Char::{Null, CharacterTabulation, CarraigeReturn, LineFeed, ReverseSolidus, Apostrophe}` to `'\0'`, `'\t'`, `'\r'`, `'\n'`, `'\\'` and `'\''` respectively. these are the same escape codes as `<char as Debug>::fmt` uses.
 - if `u8::is_ascii_control` is false, print the character wrapped in single quotes.
 - otherwise, print in the format `'\xAB'` where `A` and `B` are the hex nibbles of the byte. (`char` uses unicode escapes and this seems like the corresponding ascii format).

Tracking issue: rust-lang#110998

…=dtolnay

Stabilize the `Saturating` type

Closes rust-lang#87920
Closes rust-lang#92354

Stabilization report rust-lang#87920 (comment)
FCP rust-lang#87920 (comment)

…=compiler-errors

add diagnostic for raw identifiers in format string

Format strings don't support raw identifiers (e.g. `format!("{r#type}")`), but they do support keywords in the format string directly (e.g. `format!("{type}")`). This PR improves the error output when attempting to use a raw identifier in a format string and adds a machine-applicable suggestion to remove the `r#`.

fixes rust-lang#115466

…r-errors

improve PassMode docs

…ble, r=compiler-errors

Migrate `compiler/rustc_hir_typeck/src/callee.rs` to translatable diagnostics