arch: sim: Add BabbleSIM Support

[LingaoM]

Summary

This PR improves the Linux sim target for host-side Bluetooth testing.

It adds optional BabbleSim discrete-time support to arch/sim. When
CONFIG_SIM_BSIM_TIME is enabled, the simulator joins a BabbleSim PHY as a
device and uses the BabbleSim PHY wait protocol as the monotonic time source.
host_sleepuntil() advances through PB_MSG_WAIT requests instead of Linux
wall-time sleeps, so NuttX SIM applications can run in the same discrete-time
domain as other BabbleSim devices.

The PR also fixes the simulated HCI socket watchdog lifetime. The receive
watchdog is now started only after the host HCI socket has been opened
successfully, and is canceled on close/free. This keeps the polling lifetime
tied to the actual host socket lifetime and avoids polling an invalid host fd.

Finally, it adds a runtime HCI socket target option. --bt-dev=hciN overrides
CONFIG_SIM_HCISOCKET_DEVID for the BlueZ HCI user channel, while
--bt-dev=/path/to/socket connects the simulator to an H:4 stream over a Unix
domain socket. Omitting --bt-dev keeps the existing configured default
behavior.

Impact

• CONFIG_SIM_BSIM_TIME is disabled by default.
• Existing sim builds keep their current wall-time behavior unless
  CONFIG_SIM_BSIM_TIME is enabled.
• BabbleSim time support is limited to Linux host SIM, CONFIG_SIM_WALLTIME_SLEEP,
  and non-SMP builds.
• Building with CONFIG_SIM_BSIM_TIME=y requires:
  • BSIM_COMPONENTS_PATH for BabbleSim headers.
  • BSIM_OUT_PATH or BSIM_LIBS_DIR for BabbleSim libraries.
• The BabbleSim PHY process must be started externally by the test runner before
  launching the NuttX SIM binary.
• RTC/realtime reads still use the host realtime clock. BabbleSim is used only
  for monotonic time after the simulator joins the PHY.
• --bt-dev=hciN keeps the BlueZ user-channel path and still requires the
  normal host permissions/capabilities for BlueZ HCI access.
• --bt-dev=/path/to/socket allows use of a Unix-socket HCI transport, which can
  connect to another host process or a UART-to-Unix-socket bridge without
  requiring BlueZ raw HCI privileges for the NuttX process.
• The HCI watchdog change only affects the simulated HCI socket driver lifetime
  handling and does not change the HCI packet format or public Bluetooth APIs.

Testing

Host machine:

• Ubuntu 22.04 x86_64

Style checks:

$ git diff --check HEAD~2..HEAD
$ PATH=/home/mi/bsim-auto-test/.venv/bin:$PATH \
  ./tools/checkpatch.sh -c -u -m -g HEAD~2..HEAD

Default SIM smoke test:

$ ./tools/configure.sh -l -a ../nuttx-apps sim:nsh
$ make -j16
$ printf 'help\npoweroff\n' | timeout 20s ./nuttx

BabbleSim-enabled build:

$ kconfig-tweak --file .config \
    -e SIM_WALLTIME_SLEEP \
    -d SIM_WALLTIME_SIGNAL \
    -e SIM_BSIM_TIME
$ make olddefconfig
$ BSIM_OUT_PATH=/tmp/bsworld/build/babblesim/bsim \
  BSIM_COMPONENTS_PATH=/tmp/bsworld/build/babblesim/bsim/components \
  make -j16

BabbleSim time smoke test without a controller:

$ bs_2G4_phy_v1 -s=<sid> -D=1 -defmodem=BLE_simple -nodump
$ printf 'usleep 1000000\npoweroff\n' | \
  ./nuttx --sim-bsim-sid=<sid> \
          --sim-bsim-pid=2G4 \
          --sim-bsim-dev=0

Observed result:

The 1 second simulated sleep completed in 19 ms wall time when no handbrake
device was present.

BabbleSim handbrake verification:

$ bs_2G4_phy_v1 -s=<sid> -D=2 -defmodem=BLE_simple -nodump
$ bs_device_handbrake -s=<sid> -p=2G4 -d=1 -pp=50000 -r=1
$ printf 'usleep 1000000\npoweroff\n' | \
  ./nuttx --sim-bsim-sid=<sid> \
          --sim-bsim-pid=2G4 \
          --sim-bsim-dev=0

Observed result:

The same 1 second simulated sleep completed in 985 ms wall time with the
handbrake device registered.
A shorter 200 ms check completed in 27 ms without handbrake and 172 ms with
handbrake.

This verifies that NuttX SIM monotonic time advances through the BabbleSim PHY
and that the BabbleSim handbrake affects the NuttX SIM device.

Verified cleanup still works after enabling CONFIG_SIM_BSIM_TIME and without
exporting BabbleSim environment variables:

$ make distclean

HCI socket watchdog and runtime target tests:

Board/config:

- sim:bthcisock

Clean build:

$ make distclean
$ ./tools/configure.sh -l -a ../../nuttx-apps sim:bthcisock
$ kconfig-tweak --file .config --set-val STACK_USAGE_WARNING 0
$ make olddefconfig
$ make -j16

Default startup smoke test:

$ printf 'poweroff\n' | timeout 10s ./nuttx

Observed result:

The simulator reached NSH and powered off cleanly. When no host HCI controller
was available through the default BlueZ target, the board reported
sim_bthcisock_register() failure and continued booting without an invalid-fd
watchdog crash.

Invalid runtime argument smoke test:

$ ./nuttx --bt-dev=invalid

Observed result:

The command exited with status 1 and reported the invalid target without
crashing before nx_start().

Unix socket HCI smoke test:

$ socat -d -d UNIX-LISTEN:/tmp/hci.sock,fork,reuseaddr \
  /dev/ttyACM2,b1000000,raw,echo=0,crtscts=1

$ printf 'ifconfig\nbt bnep0 info\npoweroff\n' | \
  timeout 20s ./nuttx --bt-dev=/tmp/hci.sock

Observed result:

The simulator registered the Bluetooth network device as bnep0, and
bt bnep0 info read controller state through the Unix-socket HCI path, including
BDAddr aa:bb:cc:dd:ee:ff from the attached controller.

[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb