* adjust the default spacing so that its small enough that 5 bubbles
can show on crosshatch (5 is the default)
* Add max bubbles to BubblePositioner, replace the other usages
Test: atest BubbleDataTest
Test: manual - have 5 bubbles
- adjust screen size to largest
- open the stack
=> notice that the number of bubbles have changed and
they all fit on the screen without overlap
- repeat & check the different densities
Bug: 187715444
Change-Id: I4794ed89541eeb573c367748f980cf7ffe45d3f3
238f122f47