Prepare for 3.12.0 release

[mjcarroll]

Signed-off-by: Michael Carroll [email protected]

🎈 Release

Preparation for <3.12.0>release.

Comparison to <3.11.1>: ignition-common3_3.11.1...ign-common3

Needed by gazebosim/gz-launch#97

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 ignition-release (as needed):

Note to maintainers: Remember to use Squash-Merge

[mjcarroll]

Actually, I need to expand the changelog for this, give me a few minutes.

[codecov]

Codecov Report

Merging #195 (886bc6e) into ign-common3 (48c64a0) will not change coverage.
The diff coverage is n/a.

❗ Current head 886bc6e differs from pull request most recent head 7666fb7. Consider uploading reports for the commit 7666fb7 to get more accurate results

@@             Coverage Diff              @@
##           ign-common3     #195   +/-   ##
============================================
  Coverage        75.16%   75.16%           
============================================
  Files               72       72           
  Lines            10237    10237           
============================================
  Hits              7695     7695           
  Misses            2542     2542           

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[chapulina]

LGTM with the expanded changelog