Issue #5830 Remove com.sun.nio.file import.

This is acheived by using the 3-arg Class.forName() method call.
The bnd tool which generates the osgi manifests doesn't seem to
include Import-Package statements for the 3-arg method call, but
does for the 1-arg method call. The speculative loading of the
com.sun.nio.file.SensitivityWatchEventModifier will probably be
removed in jetty-10 onwards.

Signed-off-by: Jan Bartel <janb@webtide.com>

jetty-util/src/main/java/org/eclipse/jetty/util/PathWatcher.java

@@ -948,7 +948,7 @@ private void createWatchService() throws IOException
             {
                 nativeService = false;
                 LOG.info("Using Non-Native Java {}", pollingWatchServiceClass.getName());
-                Class<?> c = Class.forName("com.sun.nio.file.SensitivityWatchEventModifier");
+                Class<?> c = Class.forName("com.sun.nio.file.SensitivityWatchEventModifier", false, cl);
                 Field f = c.getField("HIGH");
                 modifiers = new WatchEvent.Modifier[]
                     {