Prepare for 13.0.0~pre2 Release

[azeey]

🎈 Release

Preparation for 13.0.0~pre2 release.

Comparison to gz-transport12: https://github.com/gazebosim/gz-transport/compare/gz-transport12...gz-transport13

Checklist

• [ ] Asked team if this is a good time for a release
• [ ] There are no changes to be ported from the previous major version
• [ ] No PRs targeted at this major version are close to getting in
• [ ] Bumped minor for new features, patch for bug fixes
• [ ] Updated changelog
• [ ] Updated migration guide (as needed)
• [ ] Link to PR updating dependency versions in appropriate repository in gazebo-release (as needed):

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[bot]]

Codecov Report

Merging #447 (0eaa599) into gz-transport13 (19f642d) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 0eaa599 differs from pull request most recent head fb53321. Consider uploading reports for the commit fb53321 to get more accurate results

@@               Coverage Diff               @@
##           gz-transport13     #447   +/-   ##
===============================================
  Coverage           87.76%   87.76%           
===============================================
  Files                  59       59           
  Lines                5696     5696           
===============================================
  Hits                 4999     4999           
  Misses                697      697