Macros for generating cmd*.rb , conf/*.yaml files

[harshmahesheka]

🎉 New feature

Closes #72

Summary

Added Macros for generating cmd.rb and conf/.yaml files which decreases boilerplate code from repositories.

Checklist

• [x] Signed all commits for DCO
• [x] Added tests
• [ ] Added example and/or tutorial
• [ ] Updated documentation (as needed)
• [ ] Updated migration guide (as needed)
• [ ] codecheck passed (See contributing)
• [ ] All tests passed (See test coverage)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

  Test It

  I have replaced the boilerplate code with macros in my fork here. You can build this and confirm that the correct cmd and conf are being generated and installed.

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[harshmahesheka]

So I've done a cursory pass of the macros and there are some minor knits I've pointed out. The bigger question is have you used these macros anywhere? How can I test that they run correctly? If you'd like you can create forks of the libraries and point me to branches where you are using them.

As a good rule of thumb, always include instructions on how to test your code in the PR description.

I have resolved all the knits and added instructions for testing it with ign-transport.I will try to think of some better names

[harshmahesheka]

As discussed I am closing this pr and opening another one here https://github.com/gazebosim/gz-cmake/pull/270