List gets split when widget is pasted/dropped into the list item

[FilipTokarski]

📝 Provide detailed reproduction steps (if any)

1. Switch to ck/10812-document-list-editing
2. Create a list with few items and a table outside of the list
3. Select the table and copy/paste or drag it into one of the list items

✔️ Expected result

I'd expect that it gets inserted into the list item, without splitting the list in two.

❌ Actual result

List gets split into two separate lists.

❓Screencast

0_image7.mp4

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[Reinmar]

Let's merge into #11547.