apps/system/microros: add empty library skeleton

[arjav1528]

Note: Please adhere to Contributing Guidelines.

Summary

Establish the directory structure and build system integration for micro-ROS
library in NuttX apps. This PR adds the foundational skeleton for Phase 2 of
the micro-ROS integration project—Kconfig with full configuration options for
ROS 2 distribution selection, transport layer choice (UDP/serial), agent
addressing, and resource limits. Makefile follows standard NuttX pattern using
MENUDESC and Directory.mk.

Impact

Build System:

• Adds apps/system/microros/ as new system module
• Integrates via existing parent Make.defs wildcard include
• Auto-discovered by mkkconfig.sh Kconfig generation

Configuration:

• Introduces CONFIG_SYSTEM_MICROROS menuconfig option (bool, default n)
• Adds 13 subordinate configuration options:
  • MICROROS_DISTRO: ROS 2 distribution (humble, jazzy, kilted)
  • MICROROS_TRANSPORT_UDP / MICROROS_TRANSPORT_SERIAL: transport selection
  • MICROROS_AGENT_IP, MICROROS_AGENT_PORT: UDP agent addressing
  • MICROROS_SERIAL_DEVICE, MICROROS_SERIAL_BAUD: serial transport config
  • MICROROS_MAX_NODES, MICROROS_MAX_PUBLISHERS, MICROROS_MAX_SUBSCRIPTIONS,
    MICROROS_MAX_SERVICES, MICROROS_MAX_CLIENTS: resource limits
• Proper dependencies declared (NET_UDP || SERIAL_TERMIOS for main config)
• Sensible defaults (distro=jazzy, transport=UDP, conservative resource limits)

Testing

Host Environment:

• OS: macOS 13.x + Ubuntu 26.04 (EC2)
• Build tools: gcc, make, colcon (installed)
• NuttX source: apache/nuttx master branch
• NuttX apps: apache/nuttx-apps master branch

Target Verification:

• Configuration: sim:nsh (simulator, no hardware needed)
• Board: sim (Kconfig structure only, not full cross-compilation)

Test Procedure:

# 1. Configure NuttX with sim:nsh and apps directory
cd nuttx
./tools/configure.sh sim:nsh -a ../apps

# 2. Enable micro-ROS library configuration
kconfig-tweak --enable CONFIG_SYSTEM_MICROROS

# 3. Attempt build to verify no errors
make -j$(nproc)

# Expected output: Configuration succeeds, make completes without errors

[xiaoxiang781216]

@arjav1528 could you add CMake support too?

[arjav1528]

@arjav1528 could you add CMake support too?

done, added

[acassis]

@arjav1528 very nice! Please create a documentation inside repository nuttx/Documentation/

[arjav1528]

@arjav1528 very nice! Please create a documentation inside repository nuttx/Documentation/

sure, will do, but like I am planning to do the documentation in my last and final PR, like after completing all the integration