refactor(tier4_perception_msgs): rename traffic_signal to traffic_light

[miursh]

Description

• Rename traffic_signal to traffic_light

Related Links

• MUST BE MERGED BEFORE refactor(tier4_perception_msgs): rename traffic_signal to traffic_light autowarefoundation/autoware_universe#6375
• INTERNAL discussion link

Remarks

Pre-Review Checklist for the PR Author

PR Author should check the checkboxes below when creating the PR.

• Code is properly formatted
• Assign PR to reviewer

Checklist for the PR Reviewer

Reviewers should check the checkboxes below before approval.

• Commits are properly organized and messages are according to the guideline
• Code is properly formatted
• PR title describes the changes

Post-Review Checklist for the PR Author

PR Author should check the checkboxes below before merging.

• All open points are addressed and tracked via issues or tickets
• Write release notes

CI Checks

• Build and test for PR: Required to pass before the merge.
• Check spelling: NOT required to pass before the merge. It is up to the reviewer(s). See here if you want to add some words to the spell check dictionary.

[yukkysaito]

LGTM