Rollup merge of #67741 - estebank:point-at-pat-def, r=Centril

When encountering an Item in a pat context, point at the item def

```
error[E0308]: mismatched types
  --> $DIR/const-in-struct-pat.rs:8:17
   |
LL | struct foo;
   | ----------- `foo` defined here
...
LL |     let Thing { foo } = t;
   |                 ^^^ expected struct `std::string::String`, found struct `foo`
   |
   = note: `foo` is interpreted as a unit struct, not a new binding
help: you can bind the struct field to a different name
   |
LL |     let Thing { foo: other_foo } = t;
   |                 ^^^^^^^^^^^^^^
```
```
error[E0308]: mismatched types
  --> $DIR/const.rs:14:9
   |
LL | const FOO: Foo = Foo{bar: 5};
   | ----------------------------- constant defined here
...
LL |         FOO => {},
   |         ^^^
   |         |
   |         expected `&Foo`, found struct `Foo`
   |         `FOO` is interpreted as a constant, not a new binding
   |         help: use different name to introduce a new binding: `other_foo`
```

Fix #55631, fix #48062, cc #42876.

src/test/ui/issues/issue-33504.stderr

@@ -1,8 +1,15 @@
 error[E0308]: mismatched types
   --> $DIR/issue-33504.rs:7:13
    |
+LL | struct Test;
+   | ------------ unit struct defined here
+...
 LL |         let Test = 1;
-   |             ^^^^ expected integer, found struct `Test`
+   |             ^^^^
+   |             |
+   |             expected integer, found struct `Test`
+   |             `Test` is interpreted as a unit struct, not a new binding
+   |             help: introduce a new binding instead: `other_test`
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-4968.stderr

@@ -1,8 +1,15 @@
 error[E0308]: mismatched types
   --> $DIR/issue-4968.rs:5:16
    |
+LL | const A: (isize,isize) = (4,2);
+   | ------------------------------- constant defined here
+LL | fn main() {
 LL |     match 42 { A => () }
-   |                ^ expected integer, found tuple
+   |                ^
+   |                |
+   |                expected integer, found tuple
+   |                `A` is interpreted as a constant, not a new binding
+   |                help: introduce a new binding instead: `other_a`
    |
    = note: expected type `{integer}`
              found tuple `(isize, isize)`

src/test/ui/issues/issue-5100.stderr

@@ -1,6 +1,9 @@
 error[E0308]: mismatched types
   --> $DIR/issue-5100.rs:8:9
    |
+LL | enum A { B, C }
+   |          - unit variant defined here
+...
 LL |     match (true, false) {
    |           ------------- this expression has type `(bool, bool)`
 LL |         A::B => (),

src/test/ui/issues/issue-7867.stderr

@@ -1,6 +1,9 @@
 error[E0308]: mismatched types
   --> $DIR/issue-7867.rs:7:9
    |
+LL | enum A { B, C }
+   |          - unit variant defined here
+...
 LL |     match (true, false) {
    |           ------------- this expression has type `(bool, bool)`
 LL |         A::B => (),