Inconsistent use of the 255 = uninitialized EEPROM byte pattern

[algernon]

We're mostly using EEPROMSettings.EEPROM_UNINITIALIZED_BYTE correctly, but some places use _StorageProps::uninitialized_byte, or still hard-code 255. We should settle on using one, and use that consistently.

I believe the correct thing would be to use _StorageProps::uninitialized_byte, which would need to be exposed through Runtime.storage().

Places where we use a hardcoded value:

https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/src/kaleidoscope/plugin/AccessTransientLEDMode.h#L36 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/src/kaleidoscope/plugin/LEDControl.cpp#L35 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/src/kaleidoscope_internal/LEDModeManager.cpp#L30-L32 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/plugins/Kaleidoscope-EEPROM-Settings/src/kaleidoscope/plugin/EEPROM-Settings.h#L41-L46 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/plugins/Kaleidoscope-EEPROM-Settings/src/kaleidoscope/plugin/EEPROM-Settings.h#L78 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/plugins/Kaleidoscope-EEPROM-Settings/src/kaleidoscope/plugin/EEPROM-Settings.cpp#L36-L57 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/plugins/Kaleidoscope-EEPROM-Settings/src/kaleidoscope/plugin/EEPROM-Settings.cpp#L113-L118 https://github.com/keyboardio/Kaleidoscope/blob/f5639dd5ba6d5d573d38a44158957916af2aaaea/plugins/Kaleidoscope-IdleLEDs/src/kaleidoscope/plugin/IdleLEDs.cpp#L84-L86