Pin compiled code of HOME app

Keeping the code in memory of the currently set home app is
important for latency as we don't have any kind of starting
window/splash screen when pressing the home app to hide any latency.

Memory impact:

Pinning dex/vdex:

In practical scenarios, this should be < 500kb.
The home app is usually profile-speed compiled, for which the
resulting dex/vdex files are about 2 mb. However, during regular
use, at least 1.5 MB of it is referenced in memory. This makes
sense: By definition profile-speed only compiles the things that
is usually frequently executed during regular execution.

Pinning apk:
With Launcher 3 in practical scenarios this should be about 3.7 MB,
as the APK is about 5.7 MB but 2 MB are usually referenced in any
case.

Bug: 111132016
Bug: 78585335
Test: Inspect "adb shell dumpsys pinner" after boot.
Test: Check for pinned files after updating camera/home.
Test: Check for pinned files after user switch with different
default apps.
Test: Check for pinned files after bg-dexopt.
Test: Check for pinned files after bg-dexopt + kill pid.

Change-Id: I6cdbc06d089efeb1c72a51216879ba0573502009