Remove CryptKeeperSettings

FDE support has been removed in favor of FBE, so remove the FDE settings
from the "Encryption & credentials" page of the Settings app.

For now I didn't change the way the page appears on devices that don't
use FDE; as before, it still lists "Encrypt phone", followed by either
"Encrypted" or "Phone not encrypted" with no changeable settings.  Note
that the strings used for this have "crypt_keeper" in their names but
aren't specific to FDE; the next CL will rename them.

Test: On Cuttlefish with and without encryption enabled, tested visiting
      the "Encryption & credentials" settings.
Bug: 208476087
Change-Id: I3ce9894291ea1f1886f21980a86a92bfce38038a

src/com/android/settings/Settings.java

@@ -255,7 +255,6 @@ public class Settings extends SettingsActivity {
     public static class BatterySaverScheduleSettingsActivity extends SettingsActivity { /* empty */ }
     public static class AccountSyncSettingsActivity extends SettingsActivity { /* empty */ }
     public static class AccountSyncSettingsInAddAccountActivity extends SettingsActivity { /* empty */ }
-    public static class CryptKeeperSettingsActivity extends SettingsActivity { /* empty */ }
     public static class DeviceAdminSettingsActivity extends SettingsActivity { /* empty */ }
     public static class DataUsageSummaryActivity extends SettingsActivity { /* empty */ }
     public static class MobileDataUsageListActivity extends SettingsActivity { /* empty */ }