[pm] remove package name from codePath

Initially, the package name is kept in the code path of the app, for the
purpose of easy debugging. However, ever since we introduced two-level
code path to hide the package name in the mount table, the existance of
the package name in the code path is no longer very useful. To debug the
code path of an app, the best way is to use `adb shell pm path
[package_name]` instead of `ls -lR /data/app`.

In this CL, we remove the package name from the code path. The goal is
to remove the possibility of leaking package name from the code path, if
we decide to mount the entire code path to somewhere else. Since we are
not changing the structure of the code path, this small change should be
a no-op to the rest of the system.

BUG: 291212866
Test: presubmit

Change-Id: Ia11c207e80615fdcf1213d6bc664c0123eb7724e