Add user-toggleable setting to turn off display between refreshes,
which helps mitigate the sunlight fading issue on e-ink displays.
Changes:
- Add turnOffScreen parameter to HalDisplay methods
- Add fadingFix member and setFadingFix() to GfxRenderer
- Add fadingFix setting to CrossPointSettings with persistence
- Add "Sunlight Fading Fix" toggle in Display settings
- Update SDK submodule with turnOffScreen support
Cherry-picked upstream PR #522 (da4d3b5) with conflict resolution:
- Added new lib/hal/ files (HalDisplay, HalGPIO)
- Updated GfxRenderer to use HalDisplay, preserving base viewable margins
- Adopted PR #522's MappedInputManager lookup table implementation
- Updated main.cpp to use HAL while preserving custom Serial initialization
- Updated all EInkDisplay::RefreshMode references to HalDisplay::RefreshMode
This introduces a Hardware Abstraction Layer for display and GPIO,
enabling easier emulation and testing.
