Change aconfig parameter from --namespace to --package

The namespace field in aconfig is now called package, and `aconfig
create-cache --namespace ...` is now called `aconfig create-cache
--package ...`. Change the call-site accordingly.

The Soong code still uses the namespace terminology. A follow-up CL will
change the code to refer to package instead.

Bug: 285000854
Test: m nothing
Change-Id: Id787f80c1fa4ab5d4bc37410d6712aadd8833fb4