Support per-process Application class (package parser)

Now the <process> tag supports `android:name`, which takes a custom
Application class name. If omitted, the system defaults to the
class set in the <application> tag, or the default class which is
`android.app.Application`.

Bug: 197264681
Test: atest CtsProcessTest
Test: atest PackageManagerServiceUnitTests
Change-Id: Iaf336cc34fe950c4b3d8887de557857f8c23dc83