updated rclc_examples (backport #332)

[mergify]

This is an automatic backport of pull request #332 done by Mergify.
Cherry-pick of e63b644 has failed:

On branch mergify/bp/foxy/pr-332
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Changes to be committed:
	modified:   rclc_examples/CMakeLists.txt
	modified:   rclc_examples/src/example_executor.c
	renamed:    rclc_examples/src/example_executor_convenience.c -> rclc_examples/src/example_executor_only_rcl.c

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   rclc_examples/README.md

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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[codecov-commenter]

Codecov Report

Merging #333 (4a89861) into foxy (02472d6) will decrease coverage by 2.62%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             foxy     #333      +/-   ##
==========================================
- Coverage   62.93%   60.32%   -2.62%     
==========================================
  Files          13       14       +1     
  Lines        1419     1555     +136     
  Branches      416      507      +91     
==========================================
+ Hits          893      938      +45     
- Misses        337      339       +2     
- Partials      189      278      +89     

Impacted Files	Coverage Δ
...c_parameter/test/rclc_parameter/test_parameter.cpp	33.08% <0.00%> (ø)

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