fix incorrect suggestions related to parentheses in needless_return

[lapla-cogito]

close #12157

needless_return sometimes makes incorrect suggestions by omitting necessary enclosing parentheses. This PR resolves the issue by using clippy_utils::sugg::Sugg.

changelog: [needless_return]: now makes correct suggestions which require enclosing parentheses

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[samueltardieu]

Why are parentheses required here?

[lapla-cogito]

It's because without this enclosing parentheses, the suggested code won't compile (see the original issue).
However, I know this change adds some essentially unneeded parentheses like this but this is ok as far as compiling is concerned, so I wonder if there isn't a better way...

[samueltardieu]

Ok for the present case, but I really don't like the extra parentheses added as soon as there is a binary expression. What are the case we need to detect? It looks like this is any binary expression (in the sense of Sugg, where a cast is also a binary expression) whose first argument is a block (unsafe or not):

pub fn f() -> u32 {
    { 10 } + 1
}

also requires parentheses either around { 10 } or around { 10 } + 1.

Maybe we should enhance Sugg with a maybe_stmt() which would add parentheses in this case, as it looks like this is needed only when the expression happens where a statement could also be expected. What do you think?