New lint for redundant clone in `format!`

[david-mcgillicuddy-moixa]

If somebody writes format!("foo: {}", foo.clone()) is that always redundant (since format takes a reference to its arguments and then drops them instantly)? Maybe make sure it doesn't trigger on e.g. foo.clone().bar() since that isn't necessarily redundant.

I feel like this is a specific case of cloning an immutable non-owned type that you don't then retain but that'd require proper compiler support.

[david-mcgillicuddy-moixa]

Hmm I see this is probably yet another extension of #17