A space-efficient 2D matrix

Bug: Bug: 188447813

Convert WatchedSparseBooleanMatrix to use one bit per boolean, to
further reduce the storage required for large arrays.

Further unit-tests are developed to test the Watchable and Snappable
behaviors of the matrix class.

Test: atest
 * CtsContentTestCases:IntentFilterTest
 * CtsDynamicMimeHostTestCases
 * CtsRoleTestCases
 * FrameworksServicesTests:UserSystemPackageInstallerTest
 * FrameworksServicesTests:PackageManagerSettingsTests
 * FrameworksServicesTests:PackageManagerServiceTest
 * FrameworksServicesTests:AppsFilterTest
 * FrameworksServicesTests:PackageInstallerSessionTest
 * FrameworksServicesTests:ScanTests
 * UserLifecycleTests#startUser
 * UserLifecycleTests#stopUser
 * UserLifecycleTests#switchUser
 * FrameworksServicesTests:WatcherTest
 * android.appsecurity.cts.EphemeralTest
 * android.appsecurity.cts.InstantAppUserTest

Change-Id: I5e9ada0ad3057efeafa4cf4fcf4b371850ea344a