Refactor `CLI::Parser`.

Library/Homebrew/brew.rb

Library/Homebrew/brew.sh

Library/Homebrew/cli/args.rb

Library/Homebrew/cli/parser.rb

Library/Homebrew/cmd/--cellar.rb

Library/Homebrew/cmd/--prefix.rb

Library/Homebrew/cmd/--repository.rb

Library/Homebrew/cmd/analytics.rb

Library/Homebrew/cmd/cleanup.rb

Library/Homebrew/cmd/commands.rb

Library/Homebrew/cmd/config.rb

Library/Homebrew/cmd/deps.rb

Library/Homebrew/cmd/desc.rb

Library/Homebrew/cmd/doctor.rb

Library/Homebrew/cmd/fetch.rb

Library/Homebrew/cmd/gist-logs.rb

Library/Homebrew/cmd/home.rb

Library/Homebrew/cmd/info.rb

Library/Homebrew/cmd/install.rb

Library/Homebrew/cmd/leaves.rb