Fix panic in surround_replace/delete nested multi-cursor (#9815)

Test Document
-------------
```
{{

}
}

```

Steps To Reproduce
------------------
1. 2j  # move_visual_line_down
1. C   # copy_selection_on_next_line
1. mdm # surround_delete

Debug
-----
`assertion failed: last <= from', transaction.rs:597:13`

Release
-------
`called `Result::unwrap()` on an `Err` value: Char range out of bounds:
char range 18446744073709551614..18446744073709551615,
Rope/RopeSlice char length 7', ropey-1.6.1/src/rope.rs:546:37`

Description
-----------

Processing the surrounding pairs in order violates the assertion the
ranges are ordered. To handle nested surrounds all positions have to
be sorted. Also surround_replace has to track the proper replacement
character for each position.

0 files changed, 0 insertions, 0 deletions