Apps: Switch to require API instead of get API

AndroidX added new "require____()" versions of common "get___()" APIs, such as getContext/getActivity/getArguments/etc.
Rather than wrap these in something like requireNotNull(), using these APIs will allow the underlying component to try
to tell you _why_ it was null, and thus yield a better error message.

Signed-off-by: Aayush Gupta <theimpulson@e.email>