sl-tree-item label click should toggle open/close

[gap777]

What issue are you having?

Prior to v2.8, clicking the tree item label would open or close the tree item. I think it may have actually been selecting/deselecting the item, which 2.8 decoupled from open/close (which is good!). However, open/close being triggered
only by clicking on a very small icon is difficult.

Describe the solution you'd like

Clicking the label of a tree item toggles open/close.

Describe alternatives you've considered

Write JS to propagate the label click event to call the collapsed property.

[claviska]

This was by design. Please see the discussion in #1521 for details. I'm happy to continue the conversation on the thread if you have additional thoughts to add, that way others involved in the decision have a chance to see it as well.

Thanks!