Prepare for 8.0.0 Release

[azeey]

🎈 Release

Preparation for 8.0.0 release.

Comparison to 8.0.0-pre2: gz-sim8_8.0.0-pre2...gz-sim8

Needed by <PR(s)>

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]

Codecov Report

Merging #2181 (e91e815) into gz-sim8 (727eb3c) will not change coverage.
The diff coverage is n/a.

❗ Current head e91e815 differs from pull request most recent head b4a8046. Consider uploading reports for the commit b4a8046 to get more accurate results

@@           Coverage Diff            @@
##           gz-sim8    #2181   +/-   ##
========================================
  Coverage    66.04%   66.04%           
========================================
  Files          323      323           
  Lines        30719    30719           
========================================
  Hits         20287    20287           
  Misses       10432    10432