[6.x] Fix clipped floating bard toolbar in replicators

[JayGeorge]

Description of the Problem

We recently removed motion. This PR should fix the replaced overflow clipping logic reported in #13997, which was slightly different to the working motion version.

What this PR Does

• contain-paint should only be used on the outer set when it's collapsed
• For replicators I've:
  • Replaced contain-paint with overflow-clip for replicator sets, restoring a change made previously (4be1d9d)
  • overflow-clip should only be added once the set is collapsed
• Fixes Z-Index issue on floating bard toolbar #13997

Before

After

How to Reproduce

1. Add replicator field to your pages blueprint
2. Add a bard field to that replicator - set Toolbar Mode to Floating
3. Create entry, add replicator, enter content in bard, select text to make toolbar appear.

[jasonvarga]

Can you clarify why the bard set and replicator set get different treatments?