add tests for scenario_execution_gazebo

[fred-labs]

Description

Pull request checklist

• Issue created that explains the change and why it's needed
• Tests are part of the PR (for bug fixes / features)
• Docs reviewed and added / updated if needed (for bug fixes / features)
• Format and Lint checks (make check) pass locally
• PR applies Apache 2.0 License to all code files

Pull request type

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation changes
• Other (please describe)

Current behavior

New behavior

How to test

[github-actions]

Test Results

195 tests   181 ✅  21m 28s ⏱️
  9 suites   14 💤
  9 files      0 ❌

Results for commit 282c7a2.

♻️ This comment has been updated with latest results.

[github-actions]

Scenario Results

0 tests   0 ✅  0s ⏱️
0 suites  0 💤
0 files    0 ❌

Results for commit 490e22b.

♻️ This comment has been updated with latest results.