Focal CI: static checkers and doxygen linters

[chapulina]

🎉 New feature

Summary

Add cppcheck, cpplint and doxygen checks.

Test it

Focal CI on GitHub actions should return green.

Checklist

• Signed all commits for DCO
• 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

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.

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[codecov]

Codecov Report

Merging #298 (bf9f624) into ign-transport8 (07ec13a) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head bf9f624 differs from pull request most recent head 3c23f78. Consider uploading reports for the commit 3c23f78 to get more accurate results

@@               Coverage Diff               @@
##           ign-transport8     #298   +/-   ##
===============================================
  Coverage           83.81%   83.81%           
===============================================
  Files                  51       51           
  Lines                5034     5035    +1     
===============================================
+ Hits                 4219     4220    +1     
  Misses                815      815           

Impacted Files	Coverage Δ
include/ignition/transport/AdvertiseOptions.hh	100.00% <ø> (ø)
include/ignition/transport/Publisher.hh	100.00% <ø> (ø)
include/ignition/transport/RepHandler.hh	85.36% <ø> (ø)
log/include/ignition/transport/log/QueryOptions.hh	100.00% <ø> (ø)
include/ignition/transport/ReqHandler.hh	80.58% <100.00%> (ø)

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[osrf-triage]

This pull request has been mentioned on Gazebo Community. There might be relevant details there:

https://community.gazebosim.org/t/new-ignition-releases-2022-03-25-fortress-edifice-citadel/1343/1