Auto merge of #55705 - ethanboxx:master, r=SimonSapin

Make `ParseIntError` and `IntErrorKind` fully public

Why would you write nice error types if I can't read them?

# Why

It can be useful to use `match` with errors produced when parsing strings to int. This would be useful for the `.err_match()` function in my [new crate](https://crates.io/crates/read_input).

---
I could also do this for `ParseFloatError` if people think it is a good idea.
I am new around hear so please tell me if I am getting anything wrong.

diff --cc src/libcore/num/mod.rs
Simple merge