Add DataProcessor to process raw history map for UI.

- Move interpolation from DatabaseUtil
- Add the logic to wrap processed history map to BatteryLevelData
- Change ImmutableList to List in BatteryLevelData because
  ImmutableList.of doesn't support null element.

Bug: 236101687
Test: make RunSettingsRoboTests
Change-Id: I0a842f24e5481faf65f667c08a4fdc11fe2f235c