Rollup merge of #87958 - m-ou-se:closure-migration-multispan-suggestions, r=estebank

Closure migration multispan suggestions

This changes the `rust_2021_incompatible_closure_captures` lint to only suggest inserting the parts that need to be inserted, instead of suggesting to replace the entire closure by an almost identical closure with one statement added.

Before:
```
[...]
help: add a dummy let to cause `a` to be fully captured
   |
5  ~     let _ = || {
6  +         let _ = &a;
7  +         dbg!(a.0);
8  +         println!("1");
9  +         println!("2");
10 +         println!("3");
 ...
   |

[...]
help: add a dummy let to cause `b` to be fully captured
   |
14 |     let _ = || { let _ = &b; dbg!(b.0); };
   |                ~~~~~~~~~~~~~~~~~~~~~~~~~~

[...]
help: add a dummy let to cause `c` to be fully captured
   |
16 |     let _ = || { let _ = &c; dbg!(c.0) };
   |                ~~~~~~~~~~~~~~~~~~~~~~~~~
```

After:
```
[...]
help: add a dummy let to cause `a` to be fully captured
   |
5  ~     let _ = || {
6  +         let _ = &a;
   |

[...]
help: add a dummy let to cause `b` to be fully captured
   |
14 |     let _ = || { let _ = &b; dbg!(b.0); };
   |                  +++++++++++

[...]
help: add a dummy let to cause `c` to be fully captured
   |
16 |     let _ = || { let _ = &c; dbg!(c.0) };
   |                +++++++++++++           +
```

0 files changed, 0 insertions, 0 deletions