Chitu variant for disk-based update (#18264)

buildroot/share/PlatformIO/boards/chitu_F103.json

buildroot/share/PlatformIO/variants/CHITU_F103/board.cpp

buildroot/share/PlatformIO/variants/CHITU_F103/board/board.h

buildroot/share/PlatformIO/variants/CHITU_F103/ld/common.inc

...ot/share/PlatformIO/variants/CHITU_F103/ld/extra_libs.inc

...share/PlatformIO/variants/CHITU_F103/ld/stm32f103z_dfu.ld

...ot/share/PlatformIO/variants/CHITU_F103/ld/stm32f103zc.ld

...ot/share/PlatformIO/variants/CHITU_F103/ld/stm32f103zd.ld

...ot/share/PlatformIO/variants/CHITU_F103/ld/stm32f103ze.ld

...hare/PlatformIO/variants/CHITU_F103/ld/vector_symbols.inc

...droot/share/PlatformIO/variants/CHITU_F103/pins_arduino.h

buildroot/share/PlatformIO/variants/CHITU_F103/variant.h

...ot/share/PlatformIO/variants/CHITU_F103/wirish/boards.cpp

...re/PlatformIO/variants/CHITU_F103/wirish/boards_setup.cpp

...droot/share/PlatformIO/variants/CHITU_F103/wirish/start.S

...oot/share/PlatformIO/variants/CHITU_F103/wirish/start_c.c

...ot/share/PlatformIO/variants/CHITU_F103/wirish/syscalls.c

platformio.ini