Specify version code in AndroidManifest.xml

This should be the most convenient way for both make build and Android
Studio build to share the same version code.

Bug: 110741422
Test: tapas LatinIME LatinIMETests arm64 userdebug && make -j
Change-Id: I35f850c392553b2640a4c3c7398441ac28e90eca

java/AndroidManifest.xml

@@ -16,7 +16,8 @@
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
         coreApp="true"
-        package="com.android.inputmethod.latin">
+        package="com.android.inputmethod.latin"
+        android:versionCode="28">
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />

tests/AndroidManifest.xml

@@ -15,7 +15,8 @@
 -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.android.inputmethod.latin.tests">
+    package="com.android.inputmethod.latin.tests"
+    android:versionCode="28">
 
     <uses-permission android:name="android.permission.READ_CONTACTS" />