tests: clean up file system for all tests

Library/Homebrew/test/checksum_verification_test.rb

Library/Homebrew/test/cleaner_test.rb

Library/Homebrew/test/download_strategies_test.rb

Library/Homebrew/test/formula_lock_test.rb

Library/Homebrew/test/formula_pin_test.rb

Library/Homebrew/test/formula_test.rb

Library/Homebrew/test/formulary_test.rb

Library/Homebrew/test/keg_test.rb

Library/Homebrew/test/migrator_test.rb

Library/Homebrew/test/os/mac/keg_test.rb

Library/Homebrew/test/patching_test.rb

...brew/test/support/helper/integration_command_test_case.rb

Library/Homebrew/test/support/helper/test_case.rb

Library/Homebrew/test/tab_test.rb

Library/Homebrew/test/tap_test.rb

Library/Homebrew/test/uninstall_test.rb