Add littlefs file system and update Sys.IO.FileSystem and stream #149

Job	Run time
build-target (SL_STK3701A, Debug, AzureRTOS)	2m 36s
build-target (SL_STK3701A, Debug, All)	2m 21s
build-target (ST_STM32F769I_DISCOVERY, Debug, ChibiOS)	3m 35s
build-target (ST_STM32F769I_DISCOVERY, Debug, All)	7m 19s
build-target (M5Core2, Debug, ESP32)	3m 45s
build-target (M5Core2, Debug, All)	5m 38s
build-target (NXP_MIMXRT1060_EVK, Debug, FreeRTOS-NXP)	3m 1s
build-target (NXP_MIMXRT1060_EVK, Debug, All)	1m 34s
build-target (TI_CC1352R1_LAUNCHXL, Debug, TI, 915)	1m 9s
build-target (TI_CC1352R1_LAUNCHXL, Debug, All, 915)	2m 16s
	33m 14s

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