v1.5.2 - mark PrintStr::flush() as override on most platforms; upgrade tool chain

• 1.5.2 (2022-09-22)
  • Change hashDjb2(const char*) to be an inlined function instead of
    simply delegating to the template version.
    • Increases type-safety because passing an incorrect array (e.g.
      uint16_t[]) would compile without any errors, and probably not what
      the user intended since the hash function expects a NUL-terminated
      string.
  • Mark PrintStr::flush() as override.
    • The STM32 and ESP32 platforms have finally fixed their implementation
      of Print::flush() to be virtual, consistent with other Arduino
      platforms.
    • Make exception for ATTinyCore, which does not implement a
      Print::flush().
  • Upgrade tool chain
    • Upgrade Arduino CLI from 0.20.2 to 0.27.1.
    • Upgrade Arduino AVR Core from 1.8.4 to 1.8.5.
    • Upgrade STM32 Core from 2.2.0 to 2.3.0.
    • Upgrade ESP32 Core from 2.0.2 to 2.0.5.
    • Upgrade Teensyduino from 1.56 to 1.57.