* [cli] Support packageName as global option
CLI supports other package-related options (--api-package,
--model-package, --invoker-package). This aligns those options with
--package-name to avoid confusion about how to configure these options
where those are supported.
This intentionally does not apply a packageName getter/setter to
DefaultCodegen to reduce the footprint of this change.
* [gradle] Add packagName as global option
This makes packageName available as a global option, beside apiPackage,
modelPackage, and invokerPackage to reduce potential confusion about how
to configure the four of these options by generators which support them.
