Recommend `match` instead of `.map().unwrap_or_else()`

What it does

Warn against x.map(...).unwrap_or_else(...) on an Option/Result, and recommend a match instead. Similar to https://github.com/rust-lang/rust-clippy/issues/17469.

Advantage

• More readable.
• Clearer to the reader and to the compiler that the match is exhaustive.

Drawbacks

None that I can think of, other than style and personal taste.

Example

opt.map(f).unwrap_or_else(g)

Could be written as:

match opt {
    Some(x) => f(x),
    None => g(),
}

And for a Result:

match res {
    Ok(x) => f(x),
    Err(e) => g(e),
}

Comparison with existing lints

No response

Additional Context

No response

Start by reviewing the related Clippy issue #17469 and the existing lint patterns for Rust Option and Result expressions. Implement the warning for the shown map(...).unwrap_or_else(...) forms, cover both Option and Result examples, and verify the resulting diagnostics and tests.