Point at unit structs on foreign crates in type errors when they are the pattern of a binding

[estebank]

Consts and unit structs in patterns can be confusing if they are mistaken for new bindings. We already provide some context for unit structs and consts that come from the current crate, we now also point at those from foreign crates, and we properly skip cases where the pattern has type parameters which can't be confused with a new binding. Make new binding suggestion verbose.

Fix #129792.

error[E0308]: mismatched types
   --> tests/ui/suggestions/suggest-deref-in-match-issue-132784.rs:76:9
    |
 71 |     match y_mut {
    |           ----- this expression has type `&mut Box<Option<i32>>`
...
 76 |         None => {}
    |         ^^^^
    |         |
    |         expected `Box<Option<i32>>`, found `Option<_>`
    |         `None` is interpreted as a unit variant, not a new binding
    |
   ::: library/core/src/option.rs:604:5
    |
604 |     None,
    |     ---- unit variant defined here
    |
    = note: expected struct `Box<Option<i32>>`
                 found enum `Option<_>`
help: consider dereferencing to access the inner value using the Deref trait
    |
 71 |     match &**y_mut {
    |           +++
help: introduce a new binding instead
    |
 76 -         None => {}
 76 +         other_none => {}
    |

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