Move Cask fixtures to `test/support/fixtures`.

...y/Homebrew/test/support/fixtures/cask/Casks/basic-cask.rb

...y/Homebrew/test/support/fixtures/cask/Casks/booby-trap.rb

...Homebrew/test/support/fixtures/cask/Casks/container-7z.rb

...omebrew/test/support/fixtures/cask/Casks/container-air.rb

...ebrew/test/support/fixtures/cask/Casks/container-bzip2.rb

...omebrew/test/support/fixtures/cask/Casks/container-cab.rb

...omebrew/test/support/fixtures/cask/Casks/container-dmg.rb

...mebrew/test/support/fixtures/cask/Casks/container-gzip.rb

...mebrew/test/support/fixtures/cask/Casks/container-lzma.rb

...omebrew/test/support/fixtures/cask/Casks/container-pkg.rb

...omebrew/test/support/fixtures/cask/Casks/container-rar.rb

...omebrew/test/support/fixtures/cask/Casks/container-sit.rb

...brew/test/support/fixtures/cask/Casks/container-tar-gz.rb

...omebrew/test/support/fixtures/cask/Casks/container-xar.rb

...Homebrew/test/support/fixtures/cask/Casks/container-xz.rb

...t/fixtures/cask/Casks/generic-artifact-absolute-target.rb

...support/fixtures/cask/Casks/generic-artifact-no-target.rb

...t/fixtures/cask/Casks/generic-artifact-relative-target.rb

...mebrew/test/support/fixtures/cask/Casks/invalid-sha256.rb

...t/fixtures/cask/Casks/invalid/invalid-appcast-multiple.rb