we should lint on named lifetimes forced to be equal to another named lifetime

[lcnr]

fn foo<'a, 'b>(x: &'a &'b &'a ()) {} // WARN: `'a` and `'b` are equal

and

fn foo<'a: 'b, 'b: 'a>() {} // WARN: `'a` and `'b` are equal

and

struct Foo<T: 'static>(T);

fn bar<'a>(_: Foo<&'a ()>) {} // WARN: replace `'a` with `'static`

and

struct Foo<'a>(&'a ());

impl<'a> Foo<'a> {
    fn bar<'b: 'a>(&'b self) {} // WARN: `'a` and `'b` are equal
}

these should all warn that the named lifetimes are equal to some other named lifetime and should be removed.