Closes: rust-lang#57977

Note `#![unstable]` v.s. `#[unstable]`

rust-lang#44489 was closed when the `#[panic_handler]` attribute was stabilized.

`std::panic` is already stable.

`core::panic::PanicInfo` and `core::panic::Location` are stable
and can be used through that path because of a bug
in stability checking: rust-lang#15702

Stabilize `std::{rc,sync}::Weak::{weak_count, strong_count}`

* Original PR: rust-lang#56696
* Tracking issue: rust-lang#57977

Closes: rust-lang#57977

Supporting comments:

> Although these were added for testing, it is occasionally useful to have a way to probe optimistically for whether a weak pointer has become dangling, without actually taking the overhead of manipulating atomics. Are there any plans to stabilize this?

_Originally posted by @bdonlan in rust-lang#57977 (comment)

> Having this stabilized would help. Currently, the only way to check if a weak pointer has become dangling is to call `upgrade`, which is by far expensive.

_Originally posted by @glebpom in rust-lang#57977 (comment)

Not sure if stabilizing these warrants a full RFC, so throwing this out here as a start for now.

Note: per CONTRIBUTING.md, I ran the tidy checks, but they seem to be failing on unchanged files (primarily in `src/stdsimd`).

…ylan-DPC

stabilize Result::map_or

r? @SimonSapin
Closes rust-lang#66293

Add str::strip_prefix and str::strip_suffix

Introduces a counterpart for `Path::strip_prefix` on `str`.

This was also discussed in https://internals.rust-lang.org/t/pre-pr-path-strip-prefix-counterpart-in-str/11364/.

Stabilize the `core::panic` module

`std::panic` is already stable.

`core::panic::PanicInfo` and `core::panic::Location` are stable and can be used through that path because of a bug in stability checking: rust-lang#15702

fix type_name_of_val doc comment

.

…matthewjasper

Fix repetition in matches/mod.rs

r? @matthewjasper

…sper

cleanup with push_fake_read

...and make things a bit more readable.

r? @matthewjasper