Support per-process Application class (AM and client side)

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
Change-Id: I0650a4a7c75dc37c00875e4f0ac53656f1cbeac9