fix(bluetooth_monitor): synchronize L2ping status access

[elyforl]

Checklist

• I've read the contribution guidelines.
• I've searched other issues and no duplicate issues were found.
• I'm convinced that this is not my fault but a bug.

Description

L2pingService::run() reads an L2ping object's status_ while that
object's worker thread can update it. The read and writes are not
synchronized, so the service can encounter a C++ data race.

The service's main thread calls buildDeviceList(), which starts an
L2ping worker thread for each newly found device. After the function
returns, the main thread calls object->getStatus() without waiting for
the worker to finish.

Relevant locations:

• system/autoware_bluetooth_monitor/service/l2ping_service.cpp:139-145:
  the main thread takes a status snapshot.
• system/autoware_bluetooth_monitor/service/l2ping_service.cpp:249-252:
  buildDeviceList() starts the worker thread.
• system/autoware_bluetooth_monitor/service/l2ping.cpp:69-73:
  L2ping::run() creates the std::thread.
• system/autoware_bluetooth_monitor/service/l2ping.cpp:60-62,136:
  the worker writes device information and round-trip time.
• system/autoware_bluetooth_monitor/service/l2ping.cpp:170-188:
  the worker writes status fields; getStatus() copies the same object.

Expected behavior

The service should return a consistent snapshot of each device's status
while the ping worker continues running.

Actual behavior

From source inspection, getStatus() copies status_ without a lock.
The worker updates fields of the same non-atomic object, including
std::string fields, without a lock. These accesses can be concurrent,
which is undefined behavior in C++. No runtime failure has been
observed or reproduced for this report.

Steps to reproduce

1. Pair a Bluetooth device and include its address in the monitor's
   addresses parameter. Ensure bluetoothctl paired-devices lists it.
2. Start l2ping_service and launch autoware_bluetooth_monitor as
   described in the package README. The service starts an L2ping
   worker for the matching device.
3. Allow the monitor to request status repeatedly while the worker
   continues to ping the device. Each successful request reaches
   L2pingService::run() and calls object->getStatus().
4. To detect the race dynamically, run the service under ThreadSanitizer
   and inspect concurrent accesses to L2ping::status_. The exact
   scheduling, and whether a visible failure occurs, may vary.

Versions

• Autoware Universe commit:
  2e7f15416f75031ee13532417b9ab452eba94990

Possible causes

No response

Additional context

No response