feat: add traffic signals merge node

[isamu-takagi]

Description

Add converter node to change the traffic light interface between perception and planning.
This is step 1 of #2567 (comment).

Related links

#2567

Tests performed

1. Launch planning simulation and use TrafficLightPublishPanel to publish topic from TLR module.
2. Launch this package
   ros2 launch traffic_light_selector traffic_light_selector.launch.xml
3. Check merged topic
   ros2 topic echo /perception/traffic_light_selector/traffic_signals

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[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02 ⚠️

Comparison is base (06a71f6) 11.93% compared to head (b95cc29) 11.92%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2903      +/-   ##
==========================================
- Coverage   11.93%   11.92%   -0.02%     
==========================================
  Files        1321     1323       +2     
  Lines       91941    92024      +83     
  Branches    24525    24525              
==========================================
  Hits        10974    10974              
- Misses      69608    69691      +83     
  Partials    11359    11359              

Flag	Coverage Δ		*Carryforward flag
differential	0.00% <0.00%> (?)
total	11.93% <ø> (ø)		Carriedforward from 2f862d2

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
...fic_light_selector/src/traffic_light_converter.cpp	0.00% <0.00%> (ø)
...ffic_light_selector/src/traffic_light_selector.cpp	0.00% <0.00%> (ø)

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[yukkysaito]

This is only a temporary implementation, and I approve the assumption that package names, node names, etc. will be changed.