Add new discovery types

[caguero]

🎉 New feature

Summary

This pull request adds some new discovery types to the discovery message.

Test it

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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.

[codecov]

Codecov Report

Merging #322 (59e7f6d) into main (6614240) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #322      +/-   ##
==========================================
+ Coverage   95.41%   95.43%   +0.01%     
==========================================
  Files          10       10              
  Lines        1026     1030       +4     
==========================================
+ Hits          979      983       +4     
  Misses         47       47              

Impacted Files	Coverage Δ
src/Utility.cc	98.97% <100.00%> (+<0.01%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[caguero]

I know that in a regular C++ class its allowed to append a new enumeration to an existing enum without breaking ABI but does anybody know if it's safe to do it inside a protobuf? I assumed that any change in an existing message would break it but if that's not the case I could retarget it to gz-msgs9.