Add CTA tile to hub mode

In glanceable hub view mode, the CTA tile is used to customize hub mode
and can be dismissed on button click.
In glanceable hub edit mode, the CTA tile is used to add more widgets.
And the tile is not dismissable.
The tile will be displayed as the last card in the grid.

Bug: b/313462210
Flag: ACONFIG com.android.systemui.communal_hub DEVELOPMENT
Test: atest CommunalInteractorTest
Test: atest CommunalEditModeViewModelTest
Test: atest CommunalViewModelTest
Change-Id: I519f000ea25b338f896211c1932e4b1699a42669