This change includes the following:

• TCPSocket.new: Close resources in ensure
• TCPSocket.new: Remove unnecessary comments
• Socket.tcp: Make assert_separately in TestSocket more readable
• Socket.tcp: Returning instead of exiting
• Socket.tcp: Close resources in ensure
• Socket.tcp: Avoid test failures on hosts that only support IPv4
  • The changes in Avoid test failures on hosts that only support IPv4 #12213 have also been applied to Socket.tcp.