RESTRICT AUTOMERGE Fix security vulnerability in getManageSpaceActivityIntent

Use ActivityManagerInternal.getPendingIntentActivityAsApp instead of
mContext.createPackageContextAsUser to securely construct the
PendingIntent. This prevents callers from obtaining a PendingIntent
registered under the target package identity with system privileges.

Bug: 504573577
Test:
Flag: EXEMPT BUGFIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:50d6b5520df2ffe73f2bd5f5ee7265c52a0cee9e
Merged-In: I107885fe1d3203c11868c2cabbb68ed164811bbd
Change-Id: I107885fe1d3203c11868c2cabbb68ed164811bbd