- Use normal ChibiOS I2C driver.
- Move drawing code to housekeeping -- previously it was during matrix
  scan, which gets executed during bootmagic checks. However, bootmagic
  is invoked before QWIIC subsystem is enabled, which means I2C isn't
  configured yet. All I2C calls to the OLED fail with timeouts while
  bootmagic is being checked. Housekeeping ensures this is executed once
  the system has initialised and settled.
- QWIIC OLED driver: properly clear out OLED buffer when clearing screen.