fix: do not stop ignored dragleave events in grid

[tomivirkki]

Description

Grid currently stops the propagation of all native "dragleave" events which causes the issue. The propagation of "dragleave" event should only be stopped if the grid has a dropMode, in which case corresponding "dragover" and "dragenter" events are also processed by the grid dnd logic

Fixes #8476

Type of change

• Bugfix

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mshabarov]

@tomivirkki could we also pick this to 24.4 ?
It's EOL soon and would be great to release this fix as well in the last release of this branch.

[tomivirkki]

@mshabarov cherry-picked here #8503

[vaadin-bot]

This ticket/PR has been released with Vaadin 24.7.0.alpha5 and is also targeting the upcoming stable 24.7.0 version.

[vaadin-bot]

Hi @tomivirkki and @tomivirkki, when i performed cherry-pick to this commit to 23.5, i have encountered the following issue. Can you take a look and pick it manually?
Error Message:
Error: Command failed: git cherry-pick 09164e2
The previous cherry-pick is now empty, possibly due to conflict resolution.
If you wish to commit it anyway, use:

git commit --allow-empty

Otherwise, please use 'git cherry-pick --skip'

[web-padawan]

This was backported manually to 23.5 via #8640