fix(libwaterlinked): harden TCP command handling

[Kurtuveys]

Summary

This PR improves reliability of the Water Linked TCP client and callback handling.

The TCP command path had several reliability risks:

• pending_requests_ was accessed from multiple threads without locking.
• A fast DVL response could arrive before the promise was registered.
• Pending command requests could remain unresolved when the DVL did not respond.
• Pending requests were not failed explicitly when the TCP connection was lost.
• The socket could leak if connection setup failed after socket() succeeded.
• Report callback vectors could be modified while the polling thread was iterating over them.

Changes

• Protect pending_requests_ with request_mutex_.
• Register the pending promise before sending the command.
• Add command response timeout handling.
• Fail all pending commands on connection loss.
• Close the socket on constructor connection failure paths.
• Protect report callback registration and callback iteration with a mutex.

Validation

Tested with:

colcon build --packages-up-to waterlinked_dvl_driver
colcon test --packages-select libwaterlinked --event-handlers console_direct+
colcon test-result --verbose