Android: Move alert message log from Kotlin to C++

For some reason, NativeLibrary.kt calling Log for the alert message text
makes Dolphin die with a JNI error. Supposedly the jstring passed to the
logging function is invalid. I don't understand why, because the dialog
that we show right afterwards is able to read the string just fine. The
error happens even if I pass the string directly to Log without
prepending any extra text.

There's no real downside to having the logging in C++ instead of Kotlin,
so let's move it to C++ to avoid the JNI error.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/NativeLibrary.kt

@@ -480,7 +480,6 @@ object NativeLibrary {
     fun displayAlertMsg(
         caption: String, text: String, yesNo: Boolean, isWarning: Boolean, nonBlocking: Boolean
     ): Boolean {
-        Log.error("[NativeLibrary] Alert: $text")
         val emulationActivity = emulationActivityRef.get()
         var result = false