Because the `if .. {}` statement already puts the condition in
expression scope, contained blocks would be parsed as complete
statements, so any `&` binary expression whose left operand ended in a
block would lead to a non-compiling suggestion.
This adds a visitor to identify such expressions and add parentheses.
This fixes#8052.
This splits up the needless_bool tests into `fixable.rs` and
`simple.rs`. `simple.rs` contains the code that triggers the lint
diagnostic without a suggestion.
