Emit suggestion for `where &T: Trait`

[estebank]

Given:

fn foo<T>(x: T) where &T: std::io::Read {
    panic!();
}

we currently emit

error[E0637]: `&` without an explicit lifetime name cannot be used here
 --> src/main.rs:1:23
  |
1 | fn foo<T>(x: T) where &T: std::io::Read {
  |                       ^ explicit lifetime name needed here

error[E0310]: the parameter type `T` may not live long enough
 --> src/main.rs:1:27
  |
1 | fn foo<T>(x: T) where &T: std::io::Read {
  |        -                  ^^^^^^^^^^^^^ ...so that the reference type `&'static T` does not outlive the data it points at
  |        |
  |        help: consider adding an explicit lifetime bound...: `T: 'static`

'static suggestions are a lot of the time incorrect, but in this case what we can suggest is

fn foo<T>(x: T) where for<'a> &'a T: std::io::Read {

and both errors go away. Ideally we could silence the second error and have a structured suggestion for the first.

Taken from https://github.com/rust-lang/rust/pull/82194/files#r578364173

[estebank]

error[[E0637]](https://doc.rust-lang.org/nightly/error_codes/E0637.html): `&` without an explicit lifetime name cannot be used here
 --> src/main.rs:1:23
  |
1 | fn foo<T>(x: T) where &T: std::io::Read {
  |                       ^ explicit lifetime name needed here
  |
help: consider introducing a higher-ranked lifetime here
  |
1 | fn foo<T>(x: T) where for<'a> &'a T: std::io::Read {
  |                       +++++++  ++

error[[E0311]](https://doc.rust-lang.org/nightly/error_codes/E0311.html): the parameter type `T` may not live long enough
 --> src/main.rs:1:27
  |
1 | fn foo<T>(x: T) where &T: std::io::Read {
  |                           ^^^^^^^^^^^^^ ...so that the reference type `&T` does not outlive the data it points at