Fix enum naming for avoid collision (backport #242)

[mergify]

This is an automatic backport of pull request #242 done by Mergify.
Cherry-pick of ce42968 has failed:

On branch mergify/bp/foxy/pr-242
Your branch is up to date with 'origin/foxy'.

You are currently cherry-picking commit ce42968.
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Changes to be committed:
	modified:   rclc/src/rclc/executor_handle.c
	modified:   rclc/test/rclc/test_executor_handle.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   rclc/include/rclc/executor_handle.h
	both modified:   rclc/src/rclc/executor.c

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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