Fix the problem of missing signature permissions

Moving dexopt out of the package freezer so that the installer
executes setUpdatedSystemApp() before notifying the package updated,
that causes the permission service not granting signature
permission again.
To resolve this issue, restore the flag after dexopt and then set it
again after notified the package updated.

Bug: 321139675
Flag: android.content.pm.improve_install_freeze
Test: atest com.google.android.apps.nexuslauncher.imagecomparison.WidgetHomeScreenTest
Test: atest CtsPackageManagerTestCases
Test: atest CtsInstallHostTestCases
Test: atest CtsCompilationTestCases
Change-Id: Ia67fc343f8f5bd2f78dad1110a322106c937c666