Diff issue in amendments with ordered/unordered lists

[MSoeb]

Describe the bug
Amendments in an ordered/unordered list result in an incorrect diff. If new content is entered at a lower level, the diff generates a new line. This is incorrect.

Amendment text:

Amendment output with wrong diff:

How to Reproduce

1. open motions
2. create a new motion with code 1 linked below.
3. create an amendment to it in line 1-5 with Code 2 linked below.
4. --> Error with wrong new line will appear.

Code 1:

	<li>Testzeile 1<ol>
	<li>Testzeile 2<ol>
	<li>Testzeile 3</li>
	<li>Testzeile 4</li>
</ol>
</li>
<li>Testzeile 5</li>
</ol>
</li>
<li>Testzeile 6</li>
</ol>

Code 2:

	<li>Testzeile 1<ol>
	<li>Testzeile 2<ol>
	<li>Testzeile 3 Mehr Inhalt</li>
	<li>Testzeile 4</li>
</ol>
</li>
<li>Testzeile 5</li>
</ol>
</li>
</ol>

Expected behavior
If an amendment if done to a lower level list point, the diff should work correctly.

[MSoeb]

Linked this issues with Diff Meta #2956

[reiterl]

I can reproduce this.
Simplified:
motion text:

<ol><li>Test 1<ol><li>Test 2</li><li>Test 3</li></ol></li></ol>

amendment text:

<ol><li>Test 1<ol><li>Test 2 Foo</li><li>Test 3</li></ol></li></ol>

It seems like nested ol s are a problem.