Stop propagation when deploying the context menu for a project panel entry (#3965)

This PR fixes an issue where right-click on any project panel entry
would cause the context menu on the root of the project panel
(introduced in #3954) to deploy.

We need to stop propagation in the handler on the inner project panel
list items so that the click event doesn't bubble up the tree.

Release Notes:

- Fixed an issue where the project panel was always deploying the root
context menu rather than on the clicked item.