Implement native file operations

[lucasbaizer]

WebJVM should simulate a Linux-like file system within the browser. This enables the java.io.File and java.nio.Path libraries to execute normally within a browser.

[lucasbaizer]

In OpenJDK for Linux, these native methods work with File IO (I believe):

Native method: java/io/UnixFileSystem.canonicalize0(Ljava/lang/String;)Ljava/lang/String;
Native method: java/io/UnixFileSystem.getBooleanAttributes0(Ljava/io/File;)I
Native method: java/io/UnixFileSystem.checkAccess(Ljava/io/File;I)Z
Native method: java/io/UnixFileSystem.getLastModifiedTime(Ljava/io/File;)J
Native method: java/io/UnixFileSystem.getLength(Ljava/io/File;)J
Native method: java/io/UnixFileSystem.setPermission(Ljava/io/File;IZZ)Z
Native method: java/io/UnixFileSystem.createFileExclusively(Ljava/lang/String;)Z
Native method: java/io/UnixFileSystem.delete0(Ljava/io/File;)Z
Native method: java/io/UnixFileSystem.list(Ljava/io/File;)[Ljava/lang/String;
Native method: java/io/UnixFileSystem.createDirectory(Ljava/io/File;)Z
Native method: java/io/UnixFileSystem.rename0(Ljava/io/File;Ljava/io/File;)Z
Native method: java/io/UnixFileSystem.setLastModifiedTime(Ljava/io/File;J)Z
Native method: java/io/UnixFileSystem.setReadOnly(Ljava/io/File;)Z
Native method: java/io/UnixFileSystem.getSpace(Ljava/io/File;I)J
Native method: java/io/UnixFileSystem.initIDs()V
Native method: sun/nio/ch/FileDispatcherImpl.read0(Ljava/io/FileDescriptor;JI)I
Native method: sun/nio/ch/FileDispatcherImpl.pread0(Ljava/io/FileDescriptor;JIJ)I
Native method: sun/nio/ch/FileDispatcherImpl.readv0(Ljava/io/FileDescriptor;JI)J
Native method: sun/nio/ch/FileDispatcherImpl.write0(Ljava/io/FileDescriptor;JI)I
Native method: sun/nio/ch/FileDispatcherImpl.pwrite0(Ljava/io/FileDescriptor;JIJ)I
Native method: sun/nio/ch/FileDispatcherImpl.writev0(Ljava/io/FileDescriptor;JI)J
Native method: sun/nio/ch/FileDispatcherImpl.force0(Ljava/io/FileDescriptor;Z)I
Native method: sun/nio/ch/FileDispatcherImpl.seek0(Ljava/io/FileDescriptor;J)J
Native method: sun/nio/ch/FileDispatcherImpl.truncate0(Ljava/io/FileDescriptor;J)I
Native method: sun/nio/ch/FileDispatcherImpl.size0(Ljava/io/FileDescriptor;)J
Native method: sun/nio/ch/FileDispatcherImpl.lock0(Ljava/io/FileDescriptor;ZJJZ)I
Native method: sun/nio/ch/FileDispatcherImpl.release0(Ljava/io/FileDescriptor;JJ)V
Native method: sun/nio/ch/FileDispatcherImpl.close0(Ljava/io/FileDescriptor;)V
Native method: sun/nio/ch/FileDispatcherImpl.preClose0(Ljava/io/FileDescriptor;)V
Native method: sun/nio/ch/FileDispatcherImpl.closeIntFD(I)V
Native method: sun/nio/ch/FileDispatcherImpl.init()V
Native method: sun/nio/ch/IOUtil.randomBytes([B)Z
Native method: sun/nio/ch/IOUtil.makePipe(Z)J
Native method: sun/nio/ch/IOUtil.drain(I)Z
Native method: sun/nio/ch/IOUtil.configureBlocking(Ljava/io/FileDescriptor;Z)V
Native method: sun/nio/ch/IOUtil.fdVal(Ljava/io/FileDescriptor;)I
Native method: sun/nio/ch/IOUtil.setfdVal(Ljava/io/FileDescriptor;I)V
Native method: sun/nio/ch/IOUtil.fdLimit()I
Native method: sun/nio/ch/IOUtil.iovMax()I
Native method: sun/nio/ch/IOUtil.initIDs()V