v0.9.0 (The RubyKaigi 2023 Edition)

Based on the survey results from RubyKaigi 2023, support for the significantly outdated RSpec 2 and Minitest 4 has been dropped.

Changed

• (Breaking) Drop Minitest 4 support #125 @koic
• (Breaking) Drop RSpec 2 support #124 @koic
• (Breaking) Remove deprecated TEST_QUEUE_SLAVE_MESSAGE environment variable #123 @koic

Full changes since v0.8.0