R1:cae1246359c6

Dashboard Tabs: render "Move" buttons grayed out more consistently

Summary:
If you happen to create a Dashboard by retrieving other people's panels,
you were probably affected by this visual bug.

It seems that you cannot Move things, but you really can (and that is OK).

The reason is, to move things in a Parent Panel, you only need edit permission there,
and you do not need to also have edit permissions on every Child Panel.

Closes T15492

Test Plan:
- From user A:
- Create two panels - editable by…