Add File.java to forbidden APIs

This commit cuts over all of core (not quite all tests) to java.nio.Path
It also adds the file class to the core forbidden APIs to prevent its usage
What is the FilterOutputStream doing here? This one is trappy since it will write each byte one at a time by default, boxing inside a byte[]. I think the performance here is likely very bad? Shouldnt we do FilterOutputStream(BufferedOutputStream( instead to have good performance?