fix: prevent grid body from expanding on dragover

[tomivirkki]

Fixes vaadin/flow-components#1610

The core of the fix is an additional CSS rule that forces the drag-over indicator to be smaller when dragging below the last row (with allRowsVisible on). This essentially prevents the container from expanding in height and becoming scrollable.

The CSS selector required adding a new state attribute (last) for the last non-hidden body row element.

[web-padawan]

Seems like screenshots contain differences:

 ❌ grid > drag and drop > dragover below last row when all rows visible
      Error: Visual diff failed. New screenshot is 0.72% different.

[tomivirkki]

Seems like screenshots contain differences:

Ah, seems that the grid visual tests are using before (instead of beforeEach) so the differences are caused by side-effects from other tests. Didn't notice this locally since I was using it.only.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication