Long or unforced progmem strings encode through encode_progmem_bytes, which
API action strings need. The ProgmemStringRef tests move to their own file.
ProgmemStringRef now holds a StringRef, so get_name() and friendly_name_() can
keep returning const StringRef & on other platforms. External components that
return get_name() from a const StringRef & getter would otherwise return a
reference to a temporary. friendly_name_() is deprecated there, not removed.
valve_name() returned a flash pointer on ESP8266; it now follows get_name():
static_assert there, deprecated elsewhere, with valve_log_name() for logs.
J. Nick Koston