Fix responsive grid in edit mode and content padding.

The content padding is dynamic based on the available space for the
grid. Therefore we introduce a way to set the content offset from the
grid, such that it can be used for touch handling.

Bug: 378171351
Test: manually by entering edit mode in portrait and landscape with
responsive enabled.
Flag: com.android.systemui.communal_responsive_grid

Change-Id: I2eca45db33cfaa3ae8717002b1adfcd6c035c054