Rework platform version to hide codenames.

The public platform version no longer can be a codename, it is
always the most recently released platform.  A new build property
and API provides either the offical version or the current codename
as appropriate.  This will avoid breaking apps that look at the
platform version while development is under a codename.

Bug:  143175463
Test: manual
Change-Id: I711ca20c4c8ce389697e940696051a336f5fd808

src/com/android/settings/system/SystemUpdatePreferenceController.java

@@ -89,7 +89,7 @@ public class SystemUpdatePreferenceController extends BasePreferenceController {
     @Override
     public CharSequence getSummary() {
         CharSequence summary = mContext.getString(R.string.android_version_summary,
-                Build.VERSION.RELEASE);
+                Build.VERSION.RELEASE_OR_CODENAME);
         final FutureTask<Bundle> bundleFutureTask = new FutureTask<>(
                 // Put the API call in a future to avoid StrictMode violation.
                 () -> mUpdateManager.retrieveSystemUpdateInfo());