Issue Type: Bug

Deleting lines with editor.action.deleteLines acts weird with multicursor.

1. Create a file with 12 or more lines; create multicursor selections on 3 consecutive lines, with 2 selections per line (for a total of 6 selections). Run editor.action.deleteLines. I expect those three lines will be deleted, but they aren't.

2. Do the same thing, but with just one selection per line. editor.action.deleteLines still acts weird; I would expect the three cursors to collapse into a single cursor; instead there are cursors awkwardly hanging out down below.

Sublime Text handles these situations correctly; see their behavior for a good model of what should happen.

In both cases, I feel that the cursors should probably move back to the beginning of the line, but that may be years of expectation built up by using Sublime. However, that makes the cursors more predictable, which is critical with multicursor (as some cursors may be off the screen so anticipating their behavior properly is really important).

VS Code version: Code 1.29.1 (bc24f98, 2018-11-15T19:13:36.375Z)
OS version: Windows_NT x64 10.0.16299