Revert "* lib/yaml.rb: Remove Psych::EngineManager [Bug #8344]"

zzak is not the maintainer of yaml.
This reverts commit r46097.

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* properties.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46103 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* test/lib/minitest/unit.rb: Sort leaked threads and tempfiles.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46104 b2dd03c8-39d4-4d8f-98ff-823fe69b080e