Create DeviceConfig class for positioning bubbles

This change introduces a new `DeviceConfig` class that stores device configuration properties used by BubblePositioner.
This allows testing different configurations more easily without mocking, and will be followed up with a CL that converts BubblePositionerTest to bivalent.

Bug: 308004028
Test: atest BubblePositionerTest
Change-Id: I328cd4f0c946ce062609951f59a0862a7e43078f