Auto merge of #79523 - Nadrieril:fix-usize-ranges, r=varkor

Fix overlap detection of `usize`/`isize` range patterns

`usize` and `isize` are a bit of a special case in the match usefulness algorithm, because the range of values they contain depends on the platform. Specifically, we don't want `0..usize::MAX` to count as an exhaustive match (see also [`precise_pointer_size_matching`](https://github.com/rust-lang/rust/issues/56354)). The way this was initially implemented is by treating those ranges like float ranges, i.e. with limited cleverness. This means we didn't catch the following as unreachable:
```rust
match 0usize {
    0..10 => {},
    10..20 => {},
    5..15 => {}, // oops, should be detected as unreachable
    _ => {},
}
```
This PRs fixes this oversight. Now the only difference between `usize` and `u64` range patterns is in what ranges count as exhaustive.

r? `@varkor`
`@rustbot` label +A-exhaustiveness-checking