Update to support Java 17

Support class files with version 61.

Move all use of JDK 16 for testing new features to JDK 17,
leaving JDK 16 not used for testing any more.

Removed all use of --enable-preview, as no tested features are
preview on JDK 17.

Content of README.google:
Name: Java Development Kit (JDK)
URL: https://jdk.java.net/17/
Version: 17
Revision: NA
License: the GNU General Public License, version 2, with the Classpath Exception.

Description:
This is pulled directly from the website for the JDK releases that has an open source license.
Synlinks have reen resolved using `cp -rL` before uploading.
Change-Id: I9526ce07e8911c21d5ad75b628fa4ab6fe9c2f9f
diff --git a/build.gradle b/build.gradle
index 7d9e939..68b9ecd 100644
--- a/build.gradle
+++ b/build.gradle
@@ -131,9 +131,9 @@
             srcDirs = ['src/test/examplesJava11']
         }
     }
-    examplesJava16 {
+    examplesJava17 {
         java {
-            srcDirs = ['src/test/examplesJava16']
+            srcDirs = ['src/test/examplesJava17']
         }
     }
     jdk11TimeTests {
@@ -375,18 +375,18 @@
                 "third_party": ["openjdk/openjdk-9.0.4/linux",
                                 "openjdk/jdk8/linux-x86",
                                 "openjdk/jdk-11/linux",
-                                "openjdk/jdk-16/linux"],
+                                "openjdk/jdk-17/linux"],
         ],
         osx: [
                 "third_party": ["openjdk/openjdk-9.0.4/osx",
                                 "openjdk/jdk8/darwin-x86",
                                 "openjdk/jdk-11/osx",
-                                "openjdk/jdk-16/osx"],
+                                "openjdk/jdk-17/osx"],
         ],
         windows: [
                 "third_party": ["openjdk/openjdk-9.0.4/windows",
                                 "openjdk/jdk-11/windows",
-                                "openjdk/jdk-16/windows"],
+                                "openjdk/jdk-17/windows"],
         ],
 ]
 
@@ -625,10 +625,10 @@
         JavaVersion.VERSION_11,
         false)
 setJdkCompilationWithCompatibility(
-        sourceSets.examplesJava16.compileJavaTaskName,
-        'jdk-16',
-        JavaVersion.VERSION_16,
-        true)
+        sourceSets.examplesJava17.compileJavaTaskName,
+        'jdk-17',
+        JavaVersion.VERSION_17,
+        false)
 
 task compileMainWithJava11 (type: JavaCompile) {
     dependsOn downloadDeps
@@ -1597,7 +1597,7 @@
 buildExampleJarsCreateTask("Java9", sourceSets.examplesJava9)
 buildExampleJarsCreateTask("Java10", sourceSets.examplesJava10)
 buildExampleJarsCreateTask("Java11", sourceSets.examplesJava11)
-buildExampleJarsCreateTask("Java16", sourceSets.examplesJava16)
+buildExampleJarsCreateTask("Java17", sourceSets.examplesJava17)
 
 task provideArtFrameworksDependencies {
     cloudDependencies.tools.forEach({ art ->
@@ -1680,7 +1680,7 @@
     dependsOn buildExampleJava9Jars
     dependsOn buildExampleJava10Jars
     dependsOn buildExampleJava11Jars
-    dependsOn buildExampleJava16Jars
+    dependsOn buildExampleJava17Jars
     dependsOn buildExampleAndroidApi
     def examplesDir = file("src/test/examples")
     def noDexTests = [