DPM: Notify DO/PO of security updates.

We add a variant of notifyPendingSystemUpdate method which takes an
additional isSecurityPatch boolean flag. This information, if available,
will be persisted and available to device and profile owners when they
call getPendingSystemUpdate method.

Test: gts-tradefed run gts -m GtsGmscoreHostTestCases -t com.google.android.gts.devicepolicy.DeviceOwnerTest#testPendingSystemUpdate
Test: gts-tradefed run gts -m GtsGmscoreHostTestCases -t com.google.android.gts.devicepolicy.ManagedProfileTest#testPendingSystemUpdate
Bug: 33102479
Bug: 30961046
Change-Id: If3f1b765bb18a359836ac43ac9a0a9f29e9f8428