Auto merge of #122603 - estebank:clone-o-rama, r=lcnr

Detect borrow checker errors where `.clone()` would be an appropriate user action

When a value is moved twice, suggest cloning the earlier move:

```
error[E0509]: cannot move out of type `U2`, which implements the `Drop` trait
  --> $DIR/union-move.rs:49:18
   |
LL |         move_out(x.f1_nocopy);
   |                  ^^^^^^^^^^^
   |                  |
   |                  cannot move out of here
   |                  move occurs because `x.f1_nocopy` has type `ManuallyDrop<RefCell<i32>>`, which does not implement the `Copy` trait
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL |         move_out(x.f1_nocopy.clone());
   |                             ++++++++
```

When a value is borrowed by an `fn` call, consider if cloning the result of the call would be reasonable, and suggest cloning that, instead of the argument:

```
error[E0505]: cannot move out of `a` because it is borrowed
  --> $DIR/variance-issue-20533.rs:53:14
   |
LL |         let a = AffineU32(1);
   |             - binding `a` declared here
LL |         let x = bat(&a);
   |                     -- borrow of `a` occurs here
LL |         drop(a);
   |              ^ move out of `a` occurs here
LL |         drop(x);
   |              - borrow later used here
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL |         let x = bat(&a).clone();
   |                        ++++++++
```

otherwise, suggest cloning the argument:

```
error[E0505]: cannot move out of `a` because it is borrowed
  --> $DIR/variance-issue-20533.rs:59:14
   |
LL |         let a = ClonableAffineU32(1);
   |             - binding `a` declared here
LL |         let x = foo(&a);
   |                     -- borrow of `a` occurs here
LL |         drop(a);
   |              ^ move out of `a` occurs here
LL |         drop(x);
   |              - borrow later used here
   |
help: consider cloning the value if the performance cost is acceptable
   |
LL -         let x = foo(&a);
LL +         let x = foo(a.clone());
   |
```

This suggestion doesn't attempt to square out the types between what's cloned and what the `fn` expects, to allow the user to make a determination on whether to change the `fn` call or `fn` definition themselves.

Special case move errors caused by `FnOnce`:

```
error[E0382]: use of moved value: `blk`
  --> $DIR/once-cant-call-twice-on-heap.rs:8:5
   |
LL | fn foo<F:FnOnce()>(blk: F) {
   |                    --- move occurs because `blk` has type `F`, which does not implement the `Copy` trait
LL |     blk();
   |     ----- `blk` moved due to this call
LL |     blk();
   |     ^^^ value used here after move
   |
note: `FnOnce` closures can only be called once
  --> $DIR/once-cant-call-twice-on-heap.rs:6:10
   |
LL | fn foo<F:FnOnce()>(blk: F) {
   |          ^^^^^^^^ `F` is made to be an `FnOnce` closure here
LL |     blk();
   |     ----- this value implements `FnOnce`, which causes it to be moved when called
```

Account for redundant `.clone()` calls in resulting suggestions:

```
error[E0507]: cannot move out of dereference of `S`
  --> $DIR/needs-clone-through-deref.rs:15:18
   |
LL |         for _ in self.clone().into_iter() {}
   |                  ^^^^^^^^^^^^ ----------- value moved due to this method call
   |                  |
   |                  move occurs because value has type `Vec<usize>`, which does not implement the `Copy` trait
   |
note: `into_iter` takes ownership of the receiver `self`, which moves value
  --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
help: you can `clone` the value and consume it, but this might not be your desired behavior
   |
LL |         for _ in <Vec<usize> as Clone>::clone(&self).into_iter() {}
   |                  ++++++++++++++++++++++++++++++    ~
```

We use the presence of `&mut` values in a move error as a proxy for the user caring about side effects, so we don't emit a clone suggestion in that case:

```
error[E0505]: cannot move out of `s` because it is borrowed
  --> $DIR/borrowck-overloaded-index-move-index.rs:53:7
   |
LL |     let mut s = "hello".to_string();
   |         ----- binding `s` declared here
LL |     let rs = &mut s;
   |              ------ borrow of `s` occurs here
...
LL |     f[s] = 10;
   |       ^ move out of `s` occurs here
...
LL |     use_mut(rs);
   |             -- borrow later used here
```

We properly account for `foo += foo;` errors where we *don't* suggest `foo.clone() += foo;`, instead suggesting `foo += foo.clone();`.

---

Each commit can be reviewed in isolation. There are some "cleanup" commits, but kept them separate in order to show *why* specific changes were being made, and their effect on tests' output.

Fix #49693, CC #64167.

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