Recommend `match` instead of `.map().map_err()` chaining

What it does

Warn against x.map(...).map_err(...) chaining on a Result and recommend a match instead.

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

res.map(f).map_err(g)

Could be written as:

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

Comparison with existing lints

No response

Additional Context

No response

Start by reviewing existing Clippy lint implementations and tests for Result combinators, then compare their handling of chained map and map_err calls with the example in this issue. Define the lint's intended scope and diagnostics, and consider whether the proposed match is consistently clearer before adding coverage that verifies the warning and replacement guidance.