Use the message generation framework

[mjcarroll]

This updates transport to use the message generation framework from gazebosim/gz-msgs#339

[caguero]

This works for me. I guess we'll need to merge gz-msgs first and release it, that's why I won't approve yet.

[scpeters]

This works for me. I guess we'll need to merge gz-msgs first and release it, that's why I won't approve yet.

we don't need to release this; we just need nightly builds

[scpeters]

@osrf-jenkins run tests please

[scpeters]

I found some other issues in gazebosim/gz-msgs#339 (comment), and I believe they are addressed by the following PRs:

• Compute relative path for cmake extras gz-cmake#362
• Use computed relative extras path gz-msgs#359

Testing with specially-named branches:

• test ci_matching_branch/cmake_extras_install #416
• https://build.osrfoundation.org/job/ignition_transport-ci-pr_any-homebrew-amd64/1566/
• https://build.osrfoundation.org/job/ign_transport-pr-win/535/

Running protoc on C:/J/workspace/ign_transport-pr-win/ws/install/gz-msgs10//share/protos/gz/msgs/actor.proto

  --ignmsgs_out: protoc-gen-ignmsgs: The system cannot find the file specified.

  Failed to execute protoc compiler: Command
 '['C:/vcpkg/installed/x64-windows/tools/protobuf/protoc.exe',
 '--proto_path=C:/J/workspace/ign_transport-pr-win/ws/install/gz-msgs10//share/protos',
 '--plugin=protoc-gen-ignmsgs=C:/J/workspace/ign_transport-pr-win/ws/install/gz-msgs10//bin/gz-msgs10_protoc_plugin',
 '--cpp_out=C:/J/workspace/ign_transport-pr-win/ws/build/gz-transport13/gz_msgs_gen',
 '--ignmsgs_out=C:/J/workspace/ign_transport-pr-win/ws/build/gz-transport13/gz_msgs_gen',
 'C:/J/workspace/ign_transport-pr-win/ws/install/gz-msgs10/share/protos/gz/msgs/actor.proto']'
 returned non-zero exit status 1.

[scpeters]

I built a jammy nightly of gz-msgs10 (see gazebo-release/gz-msgs10-release#3 (comment)) and ran the jammy jenkins build for this branch, and it also has some test failures:

• https://build.osrfoundation.org/job/gz_transport-ci-pr_any-jammy-amd64/32/