Gutenberg: Classic block: "Paste as Text" notification uses inconsistent styles.

[kjellr]

Describe the bug

Inside of a classic block, you can toggle a "Paste as Text" button in the toolbar to paste contents as plain text. The first time you select this option, you're shown a notification that explains its functionality:

The style and placement of this notification are inconsistent with everything else in the editor — it feels broken. I wonder if we can customize it a bit so it doesn't feel so out of place?

To Reproduce
Steps to reproduce the behavior:

1. Add a Classic editor block
2. Click "More" in the classic editor toolbar to show the second row of controls.
3. Click the "Paste as Text" button in the second row of the classic editor toolbar.

_(Note that this issue does exist in the Classic Editor as well.)_

[karmatosed]

Design wise, lets use the strip message we have in place over blocks. I think ideally though yes let's get this made more inline with what we have usually.

[kjellr]

Thanks! Here's a mockup, using that pattern (Visually, it's similar to the "This block has been modified externally" message).

[karmatosed]

@kjellr that totally is what I was thinking thanks.