Refactor DeviceAdapter to extract split-ramp logic

This change updates the DeviceAdapter implementation to clear out
the step-to-ramp and ramp-to-step adapters and move the split ramp logic
to a separate adapter class.

This will make sure that long PWLE segments will always be split, even
if they're added by other adapters like the ramp-down one that has duration
configured independently from the HAL capabilities.

Fix: 292081642
Test: atest SplitSegmentsAdapterTest
Change-Id: I091e539a516985fdcf90a4e1f4d8c9dc391eb772