PackageManager lock reduction: IntentResolver

Bug: 161323622

Modify the IntentResolver classes used by PackageManagerServer to be
Watchable and Snappable.

Test: atest
 * FrameworksServicesTests:UserSystemPackageInstallerTest
 * FrameworksServicesTests:PackageManagerSettingsTests
 * FrameworksServicesTests:PackageManagerServiceTest
 * FrameworksServicesTests:AppsFilterTest
 * FrameworksServicesTests:PackageInstallerSessionTest
 * FrameworksServicesTests:ScanTests
 * FrameworksServicesTests:WatcherTest

Change-Id: Ifb243cf9da801462fdaef3bcf5786a80fac202f2