unnecessary_unwrap: should not trigger if the `is_some` is just part of the conditional

unnecessary_unwrap recommends that foo.is_some() in a conditional followed by foo.unwrap() should be replaced by an if let. That is usually good advice, however, if the is_some is just part of the conditional, then the only way to use if let is with nested ifs.

E.g.,

if some_condition && foo.is_some() {
    let foo = foo.unwrap();
    ...
}

can only be rewritten as

if some_condition {
    if let Some(foo) = foo {
        ...
    }
}

which is not much of an improvement (and arguably no improvement at all). (In this case, using match might be better, but in some more complex examples it is not possible).

I would much prefer is unnecessary_unwrap only triggered when it was possible to rewrite exactly using a single if let or match.

Start by locating the unnecessary_unwrap lint implementation and its tests in rust-clippy. Reproduce the issue with the some_condition && foo.is_some() example, then compare its behavior with a standalone conditional. Done means the lint avoids recommending a rewrite when is_some() is only part of the condition, while preserving the intended recommendation for directly rewritable cases.