Testing the operation with `pico_enable_stdio_semihosting()`

[oyama]

It is important and must be checked that it does not conflict with the following stdio hook libraries used in existing debugging

• [x] pico_enable_stdio_usb()
• [x] pico_enable_stdio_uart()
• [x] pico_enable_stdio_semihosting()

[oyama]

pico_enable_stdio_usb(main 1)
pico_enable_stdio_uart(main 1)
pico_enable_stdio_semihosting(main 1)
pico_enable_filesystem(main AUTO_INIT TRUE)

It was confirmed that stdout is output for each even when pico-vfs links are used.

Originally pico_stdio_semihosting only followed SYS_WRITE of stdout with fd = 1, so file I/O with the host is out of scope.