Prepare for 8.1.0 release

[iche033]

🎈 Release

Preparation for 8.1.0 release.

Comparison to 8.0.1: gz-sensors8_8.0.1...prep_8.1.0

Needed by gazebosim/gz-sim#2408

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

All modified and coverable lines are covered by tests ✅

Project coverage is 72.45%. Comparing base (68a50ee) to head (93833f9).
Report is 4 commits behind head on gz-sensors8.

Additional details and impacted files

@@               Coverage Diff               @@
##           gz-sensors8     #433      +/-   ##
===============================================
- Coverage        72.78%   72.45%   -0.34%     
===============================================
  Files               36       36              
  Lines             4983     5042      +59     
===============================================
+ Hits              3627     3653      +26     
- Misses            1356     1389      +33     

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