Add littlefs file system and update Sys.IO.FileSystem and stream #136

Job	Run time
build-target (SL_STK3701A, Debug, AzureRTOS)	3m 44s
build-target (SL_STK3701A, Debug, All)	6m 16s
build-target (ST_STM32F769I_DISCOVERY, Debug, ChibiOS)	1m 51s
build-target (ST_STM32F769I_DISCOVERY, Debug, All)	5m 33s
build-target (M5Core2, Debug, ESP32)	3m 0s
build-target (M5Core2, Debug, All)	5m 42s
build-target (NXP_MIMXRT1060_EVK, Debug, FreeRTOS-NXP)	1m 41s
build-target (NXP_MIMXRT1060_EVK, Debug, All)	5m 44s
build-target (TI_CC1352R1_LAUNCHXL, Debug, TI, 915)	1m 51s
build-target (TI_CC1352R1_LAUNCHXL, Debug, All, 915)	5m 49s
	41m 11s

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