Copy Line Up/Down commands do not preserve more than two multi-cursors on the same line

[goldenstein64]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.116.0-insider (user setup)
• OS Version: Windows 11

Steps to Reproduce:

1. Write a line of text, e.g. foo bar baz
2. Place at least 3 cursors on the same line from left to right with Alt+Click, e.g.
   • start with foo| bar baz,
   • follow with foo| bar| baz,
   • and finally foo| bar| baz|
3. Copy that line up or down using Shift+Alt+Up/Down Arrow

Expected: All cursors are moved to the copied line, e.g. with Shift+Alt+Down Arrow,

foo bar baz
foo| bar| baz|

Actual: Only the first cursor and the leftmost non-first cursor are moved down to the copied line, e.g.

foo bar baz
foo| bar| baz

Notice how the cursor after baz is gone.