Fix compatibility with protobuf 22

[traversaro]

🎉 New feature

Fix #404 by adding compatibility with protobuf >= 22 .

Summary

Similar to gazebosim/gz-msgs#346, but with an additional fix to change the removed google::protobuf::down_cast to google::protobuf::internal::DownCast . It may not be ideal to use a function declared in an internal:: namepsace, but that how actually the method was called in protobuf 2 when it was first used.

Test it

Install protobuf 22 or 23, and compile gz-citadel against 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.

[caguero]

Nit: Remove extra space at the end of the line to make the style checker happy.

[traversaro]

Done!

[codecov]

Codecov Report

Merging #405 (2b80785) into ign-transport8 (cb1c95b) will decrease coverage by 0.05%.
The diff coverage is 88.10%.

❗ Current head 2b80785 differs from pull request most recent head e35a697. Consider uploading reports for the commit e35a697 to get more accurate results

@@                Coverage Diff                 @@
##           ign-transport8     #405      +/-   ##
==================================================
- Coverage           83.61%   83.56%   -0.05%     
==================================================
  Files                  51       51              
  Lines                5035     5039       +4     
==================================================
+ Hits                 4210     4211       +1     
- Misses                825      828       +3     

Impacted Files	Coverage Δ
include/gz/transport/Packet.hh	0.00% <0.00%> (ø)
...og/include/gz/transport/log/detail/QueryOptions.hh	100.00% <ø> (ø)
log/src/Batch.cc	89.28% <ø> (ø)
log/src/Descriptor.cc	89.65% <ø> (ø)
log/src/Descriptor.hh	100.00% <ø> (ø)
log/src/Log.cc	78.72% <ø> (ø)
log/src/Message.cc	100.00% <ø> (ø)
log/src/MsgIter.cc	80.43% <ø> (ø)
log/src/QualifiedTime.cc	97.81% <ø> (ø)
log/src/QueryOptions.cc	100.00% <ø> (ø)
... and 40 more

it's fixed