Refactor conditional ROS_DISTRO_GALACTIC include with __has_include

[ralwing]

Checklist

• I've read the contribution guidelines.
• I've searched other issues and no duplicate issues were found.
• I've agreed with the maintainers that I can plan this task.

Description

Replace

#ifdef ROS_DISTRO_GALACTIC

with

#if __has_include

where applicable

Purpose

This will release code from environmentall variables and also make it more readable and easier to configure, and still galactic/humble compatible.

Possible approaches

Refactor code

Definition of done

All conditional includes replaced with suggested change.

[kenji-miyake]

Wrote my concerns here: #2236 (comment)

This will release code from environmentall variables and also make it more readable and easier to configure,

@ralwing Could you explain the reason why you felt so? I feel it's not clear.
Also, does environment variables cause any problem?