healthd: restructure healthd_mode_charger

Refactor drawing code into separate class, and allow for split screen
drawing with offset.

Cherry picked from commit 7f386dcab98b4a2827b5ffe29d7d3de7637841c0

Bug: 63541890
Test: Verify charging mode animation
Change-Id: I6c089460f55b8c2f75f4aa3153a5736f6f434b51
4 files changed