SPIFFS has been a great filesystem, but it has significant problems in
many cases (and it's also pretty slow).  Development seems to have
slowed/stopped on the upstream version, and we're not able to provide
support or fix the known issues with it as-is.

Deprecate SPIFFS variable.

Update all examples to use LittleFS instead of SPIFFS.

Also, minor cleanup on very old examples which has obsolete delays
waiting for the Serial port to come up, or which were stuck at 9600 baud
because of their ancient AVR heritage.

Fixes esp8266#7095

mcspr mentioned this pull request