Support installation of the new app source certificate

The new certificate can be installed from Settings ("Install a
certificate > App Source certificate").  The installation flow includes
a warning with user authorization to proceed, then a prompt for reboot
(now or later).

Installed certificate can be managed in "User credentials".  The name is
currently a hash of hex numbers.

Upon deletion, there will also be a promot for reboot (now or later).

Test: Only see the new setting entry if feature is enabled
Test: Install from Settings, see the expected file name in
      /data/misc/keysetore/user_0.  Reboot also works.
Test: Able to see the certificate in Settings after installed
Test: Able to delete the certificate, which triggers confirmation dialog
      to reboot.  Reboot works.
Test: add certificate, see dialog, "not now" / tapping elsewhere does
      nothing
Test: atest RestrictedEncryptionPreferenceControllerTest
Bug: 112038744

Change-Id: I7a4494ea0f243730df2212076588074d8774ae23

src/com/android/settings/security/InstallCaCertificateWarning.java

@@ -46,7 +46,7 @@ public class InstallCaCertificateWarning extends Activity {
         final FooterBarMixin mixin = layout.getMixin(FooterBarMixin.class);
         mixin.setSecondaryButton(
                 new FooterButton.Builder(this)
-                        .setText(R.string.ca_certificate_warning_install_anyway)
+                        .setText(R.string.certificate_warning_install_anyway)
                         .setListener(installCaCertificate())
                         .setButtonType(FooterButton.ButtonType.OTHER)
                         .setTheme(R.style.SudGlifButton_Secondary)
@@ -55,7 +55,7 @@ public class InstallCaCertificateWarning extends Activity {
 
         mixin.setPrimaryButton(
                 new FooterButton.Builder(this)
-                        .setText(R.string.ca_certificate_warning_dont_install)
+                        .setText(R.string.certificate_warning_dont_install)
                         .setListener(returnToInstallCertificateFromStorage())
                         .setButtonType(FooterButton.ButtonType.NEXT)
                         .setTheme(R.style.SudGlifButton_Primary)