v1.2.3 - add enableTerminalEcho(); upgrade to using pre-installed LittleFS library on ESP32>=2.0.0; add notes about using Valgrind

• 1.2.3 (2022-02-24)
  • Rename unixhostduino_main() to epoxyduino_main(), and make it
    static. No need to expose it publicly.
  • Add enableTerminalEcho() function to enable terminal echoing.
    See Enable Terminal Echo.
  • Update examples and EpoxyFS/README.md to be
    compatible with new LittleFS library in ESP32 >=2.0.0.
  • Add EpoxyFS/SeekBenchmark to
    measure the performance loss of calling seek() before a read().
    • Sometimes the client-code is simpler when reading multiple records
      if it can call seek() with an explicit offset before each read().
    • The alternative would be calling read() multiple times sequentially
      and using its internal cursor to advance automatically.
    • This benchmark shows that seek() causes significant performance
      loss, even if the seek() offset is identical to the internal cursor,
      so might be expected to be optimized away.
  • Add notes about Debugging tools and options
    under a Unix environment, such as Valgrind.