Fix duplicate symbol error for collect_metrics flag in offline_node (Issue #80)

[discodyer]

Description

This PR fixes a compilation issue caused by duplicate definition of the collect_metrics gflags flag.

Issue

as issue #80 said, running cartographer_ros fails with the following error:

 [cartographer_node-2] ERROR: flag 'collect_metrics' was defined more than once (in files '/home/.../cartographer_ws/src/cartographer_ros/cartographer_ros/src/offline_node.cpp' and '/home/.../cartographer_ws/src/cartographer_ros/cartographer_ros/src/node_main.cpp').

This occurred because src/offline_node.cpp was being linked into both the cartographer_ros shared library and the cartographer_offline_node executable, causing a symbol conflict.

Changes Made

1. Removed src/offline_node.cpp from the shared library source list to avoid duplicate symbol definitions.
2. Added src/offline_node.cpp to the cartographer_offline_node executable target.
3. Added missing urdf dependency to the offline node target.
4. Added macro definitions PRE_JAZZY_SERIALIZED_BAG_MSG_FIELD_NAME to maintain consistency.

Verification

• All targets build successfully without new warnings.
• Verified in ROS Humble environments.