system: Add stty utility for terminal control

[fangpeina]

Summary

Add a stty command to NuttX, providing a standard Unix-like interface for
viewing and configuring terminal (TTY) device settings at runtime via termios.

Impact

• Features: Adds stty utility for runtime terminal configuration
• User Experience: Users can inspect and modify TTY settings from NSH
• Build: No build system changes; new CONFIG_SYSTEM_STTY option, depends on CONFIG_SERIAL_TERMIOS

Testing

Testing on sim, qemu and physical device.

Configuration:

• Board: sim:nsh (Linux host)
• Config: CONFIG_SIM_UART_NUMBER=1, CONFIG_SIM_UART_PTY=y, CONFIG_SERIAL_TERMIOS=y, CONFIG_SYSTEM_STTY=y

Runtime Test Results(sim):

nsh> stty -F /dev/ttySIM0
/dev/ttySIM0 connected to pseudotty: /dev/pts/31
Terminal settings for /dev/ttySIM0:
  speed unknown or not supported by driver; min = 1; time = 0;
  c_iflag: 0x00000000 -icrnl -igncr -inlcr
  c_oflag: 0x00000000 -opost -onlcr -ocrnl
  c_lflag: 0x00000000 -echo -icanon -isig
  c_cflag: 0x000000bf -clocal cread -cstopb
nsh> stty -F /dev/ttySIM0 cooked
/dev/ttySIM0 connected to pseudotty: /dev/pts/31
Settings applied to /dev/ttySIM0
nsh> stty -F /dev/ttySIM0
/dev/ttySIM0 connected to pseudotty: /dev/pts/31
Terminal settings for /dev/ttySIM0:
  speed unknown or not supported by driver; min = 1; time = 0;
  c_iflag: 0x00000100 icrnl -igncr -inlcr
  c_oflag: 0x00000005 opost onlcr -ocrnl
  c_lflag: 0x0000000b echo icanon isig
  c_cflag: 0x000000bf -clocal cread -cstopb
nsh> stty -F /dev/ttySIM0 raw -echo
/dev/ttySIM0 connected to pseudotty: /dev/pts/31
Settings applied to /dev/ttySIM0
nsh> stty -F /dev/ttySIM0
/dev/ttySIM0 connected to pseudotty: /dev/pts/31
Terminal settings for /dev/ttySIM0:
  speed unknown or not supported by driver; min = 1; time = 0;
  c_iflag: 0x00000000 -icrnl -igncr -inlcr
  c_oflag: 0x00000004 -opost onlcr -ocrnl
  c_lflag: 0x00000000 -echo -icanon -isig
  c_cflag: 0x000000bf -clocal cread -cstopb
nsh> 
nsh> stty
Terminal settings for stdin:
  speed unknown or not supported by driver; min = 1; time = 0;
  c_iflag: 0x00000100 icrnl -igncr -inlcr
  c_oflag: 0x00000005 opost onlcr -ocrnl
  c_lflag: 0x0000000b echo icanon isig
  c_cflag: 0x000000bf -clocal cread -cstopb
nsh> stty -F /dev/null
ERROR: /dev/null is not a TTY
nsh> stty -F /dev/noexist
ERROR: Failed to open /dev/noexist: 2

Runtime Test Results(goldfish-armv7a-ap):

goldfish-armv7a-ap> stty -F /dev/ttyS1
Terminal settings for /dev/ttyS1:
  speed 115200 baud; min = 1; time = 0;
  c_iflag: 0x00000100 icrnl -igncr -inlcr
  c_oflag: 0x00000005 opost onlcr -ocrnl
  c_lflag: 0x0000000b echo icanon isig
  c_cflag: 0x000000b0 -clocal cread -cstopb

[acassis]

@fangpeina nice addition! Please add the Documentation about this new command

[fangpeina]

@fangpeina nice addition! Please add the Documentation about this new command

Done. Related PR: #19845