Merge `Hbc::Container` classes into `UnpackStrategy`.

Library/Homebrew/cask/lib/hbc.rb

Library/Homebrew/cask/lib/hbc/artifact.rb

Library/Homebrew/cask/lib/hbc/artifact/abstract_artifact.rb

Library/Homebrew/cask/lib/hbc/artifact/nested_container.rb

Library/Homebrew/cask/lib/hbc/audit.rb

Library/Homebrew/cask/lib/hbc/container.rb

Library/Homebrew/cask/lib/hbc/container/air.rb

Library/Homebrew/cask/lib/hbc/container/base.rb

Library/Homebrew/cask/lib/hbc/container/bzip2.rb

Library/Homebrew/cask/lib/hbc/container/cab.rb

Library/Homebrew/cask/lib/hbc/container/dmg.rb

Library/Homebrew/cask/lib/hbc/container/executable.rb

Library/Homebrew/cask/lib/hbc/container/generic_unar.rb

Library/Homebrew/cask/lib/hbc/container/gzip.rb

Library/Homebrew/cask/lib/hbc/container/lzma.rb

Library/Homebrew/cask/lib/hbc/container/naked.rb

Library/Homebrew/cask/lib/hbc/container/otf.rb

Library/Homebrew/cask/lib/hbc/container/pkg.rb

Library/Homebrew/cask/lib/hbc/container/rar.rb

...brew/cask/lib/hbc/container/self_extracting_executable.rb