R1:9ad9ac9be695

On Dashboard tab panels in edit mode, make the "Tab Name" and the "Dropdown Edit Caret" into different links

Summary:
Ref T13272. In edit mode, tab panels now have a dropdown menu. However, this sort of overrlaps with the actual action of clicking the tab to select it.

Separate these into different click targets so that "select tab X" and "open dropdown menu for X" are different operations.

This is more work than it appears because:

- We have an "action icon" already, used when you put a dashboard on…