Add DPM.getKeyPairGrants()

This CL adds the underlying method to KeyChain. The method
returns UIDs of the grantee packages.

Bug: 179180345
Test: atest com.android.cts.devicepolicy.MixedManagedProfileOwnerTest#testKeyManagement
Test: atest com.android.cts.devicepolicy.MixedDeviceOwnerTest#testDelegatedCertInstallerDirectly
Test: atest android.admin.cts.DevicePolicyManagerTest
Test: atest KeyChainTests
Test: m RunKeyChainRoboTests
Change-Id: I73529e8871fd35ddff29f4cfddae97ed47587407
Merged-In: I73529e8871fd35ddff29f4cfddae97ed47587407
4 files changed