Mass change: new preflight/postflight stanzas

Convert 61 Casks to new DSL forms
 - `before_install` to `preflight`
 - `after_install` to `postflight`
 - `before_uninstall` to `uninstall_preflight`
 - `after_uninstall` to `uninstall_postflight`

References: #6074, #5890, #4688