close hole for race condition

Has to add core_pins.h to get delayMicroseconds()
made empty while()'s on HSRUN state change have a measurable 2us wait
each iteration
added explicit 100us delay leaving HSRUN to allow internal V to
satbilize, seems CPU does this already as 10-50 us made no change, and
100 is not measurable on larger writes.
since eeprom_initialize() blindly restores interrupts amd can run under
HSRUN, moved hsrun_off()

EEPROM write on T_3.6 under HSRUN - Drop and Raise