add provisioningContext to ActiveAdmin to store metadata about when the admin was set

Test: executing tests that use dpm command with the --provisioning-context parameter
Test: executing command: dumpsys device_policy
Test: atest CtsDevicePolicyTestCases:android.devicepolicy.cts.DeviceOwnerTest#getIsProvisioningAllowed_forManagedDevice_setupWizardIsComplete_returnsFalse
Test: adb shell dpm set-device-owner --provisioning-context blabla com.android.cts.RemoteDPC/com.android.bedstead.testapp.BaseTestAppDeviceAdminReceiver
Test: atest FrameworksServicesTests:com.android.server.devicepolicy.NetworkEventTest
adb shell dpm help
Flag: android.app.admin.flags.provisioning_context_parameter
Bug: 326525847
Change-Id: I5d10812b2da9a136076d86a4b6dfe8f6c5b8a7d0