Rollup merge of #91346 - ibraheemdev:result-inspect, r=dtolnay

Rollup merge of #91346 - ibraheemdev:result-inspect, r=dtolnay

Add `Option::inspect` and `Result::{inspect, inspect_err}`

```rust
// core::result

impl Result<T, E> {
    pub fn inspect<F: FnOnce(&T)>(self, f: F) -> Self;
    pub fn inspect_err<F: FnOnce(&E)>(self, f: F) -> Self;
}

// core::option

impl Option<T> {
    pub fn inspect<F: FnOnce(&T)>(self, f: F) -> Self;
}
```