Fix DDS init on modern kernels: idempotent ChannelFactory.Init + relax cyclonedds pin

[PhysicistJohn]

Problem

On Ubuntu 24.04 (kernel 6.x), gear_sonic/scripts/run_sim_loop.py fails at DDS initialization in two stacked ways:

1. cyclonedds 0.10.2 hangs. The pinned cyclonedds==0.10.2 wheel's Domain creation blocks indefinitely on recent kernels — the sim loop stalls at ChannelFactoryInitialize with no error output.

2. Double init raises on cyclonedds ≥ 11. After upgrading cyclonedds, a second failure surfaces: the sim loop initializes the channel factory from both the control-loop side and the simulator side of the same process, and cyclonedds ≥ 11 refuses to re-create a live Domain:

from unitree_sdk2py.core.channel import ChannelFactoryInitialize
ChannelFactoryInitialize(0, 'lo')   # ok
ChannelFactoryInitialize(0, 'lo')   # [ChannelFactory] create domain error.
                                    # msg: Occurred upon initialisation of a cyclonedds.domain.Domain

Fix

• ChannelFactory.Init returns early when the domain is already live — the class is already a Singleton, so a second Init in-process is safe to treat as a no-op.
• Relax the vendored SDK's pin to cyclonedds>=0.10.2,<12. The SDK runs unmodified against cyclonedds 11.x (verified: pub/sub on rt/lowstate/rt/lowcmd, channel factory init with explicit interface, on both Python 3.10 and 3.12).

Tested

• Ubuntu 24.04, kernel 6.17, RTX 6000 Ada, Python 3.10 (.venv_sim)
• Double-init snippet above passes after the patch
• run_sim_loop.py --no-enable-onscreen --enable-offscreen boots past DDS init

[PhysicistJohn]

Note: upstream unitreerobotics/unitree_sdk2_python master already carries an equivalent idempotence guard in ChannelFactory.Init (an __initialized flag with a lock), so the guard here is effectively a backport to the vendored copy — syncing external_dependencies/unitree_sdk2_python with upstream would be an equally good resolution. The cyclonedds pin relax is also filed upstream as unitreerobotics/unitree_sdk2_python#161.