Refactor battery demo

[caguero]

Refactors the battery demo leveraging the latest improvements in ros_gz.

• I replaced the logic to spawn the bridge using the RosGzBridge action.
• I left the example in Python and using Gazebo for being able to use the -z 1000000 flag.

Summary

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[ahcorde]

why not the xml version ?

[caguero]

why not the xml version ?

We're launching Gazebo with -z 1000000. If we move to XML we cannot support it.

[ahcorde]

Launch is a Python file no a xml