Make CompanionDeviceManager.apk to platform signed

Inorder to make CompanionDeviceMananger to be able to
get appInfo from non-0 profile we need to add
android.permission.INTERACT_ACROSS_USERS permission and
make CompanionDeviceManager.ap platform signed.

Fix: 215160795
Test: atest CtsCompanionDeviceManagerCoreTestCases
      atest CtsCompanionDeviceManagerUiAutomationTestCases
      atest CtsOsTestCases:CompanionDeviceManagerTest

Change-Id: I26cebadcdef05274436cd454b4d635d82eb2b7e2
diff --git a/packages/CompanionDeviceManager/Android.bp b/packages/CompanionDeviceManager/Android.bp
index 6ded1637..9f5bfd4 100644
--- a/packages/CompanionDeviceManager/Android.bp
+++ b/packages/CompanionDeviceManager/Android.bp
@@ -34,6 +34,7 @@
 android_app {
     name: "CompanionDeviceManager",
     defaults: ["platform_app_defaults"],
+    certificate: "platform",
     srcs: ["src/**/*.java"],
 
     static_libs: [