In configurations where AOSP Settings.apk is not included, there might
not be any home activity. E.g. CSI doesn't have Settings.apk.
This CL adds a null home activity to Shell.apk, which is in CSI,
so the framework can be in a sane state. Without such null home
activity in CSI, package manager fails to install any APKs.
Bug: 148044842
Test: $ lunch csi_arm64-userdebug; m -j
# Flash CSI to a Pixel (with AVB disabled) and reboot
$ m DeviceHealthChecks
$ adb install $OUT/testcases/DeviceHealthTests/arm64/DeviceHealthTests.apk
Performing Streamed Install
Success
Change-Id: I87999e30298bbe42af64f28e88fc6dc5975f1ca3
6b1c4a9e09