fix displayTest preference and add loop for testing display #1

Job	Run time
build (Arduino_GFXDemo)	17s
build (Arduino_GFX_PDQgraphicstest)	13s
build (GetBatteryVoltage)	13s
build (I2CScan)	11s
build (ImageScroll)	13s
build (MPR121TouchSensor)	3s
build (PCBClock)	1s
build (PokerS3)	1s
build (SerialExample)	1s
build (T-Display-S3-MIDI)	1s
build (TFT_Rainbow)	1s
build (factory)	10s
build (lv_demos)	8s
build (nes)	1s
build (ota)	1s
build (sd)	1s
build (tft)	1s
build (touch_test)	1s
build (usb_hid_pad)	1s
	1m 39s

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