chore(implementation)!: use Jetty-12 core without servlets

Port the invoker to upgrade to Eclipse Jetty-12 version 12.  Specifically using the new core APIs of Eclipse Jetty-12 that allow the overhead of a Servlet container to be avoided.   Several optimizations are included, including the optimization that small writes can be buffered in such a way to avoid chunked responses when possible.

BREAKING CHANGE: use Java 17 or above, as required by Eclipse Jetty-12.

Author: gregw

invoker/core/src/main/java/com/google/cloud/functions/invoker/BackgroundFunctionExecutor.java

@@ -322,8 +322,8 @@ void serviceCloudEvent(CloudEvent cloudEvent) throws Exception {
 
   /** Executes the user's background function. This can handle all HTTP methods. */
   @Override
-  public void handle(String s, Request baseRequest, HttpServletRequest req,
-      HttpServletResponse res) throws IOException, ServletException {
+  public void handle(String s, Request baseRequest, HttpServletRequest req, HttpServletResponse res)
+      throws IOException, ServletException {
     baseRequest.setHandled(true);
     String contentType = req.getContentType();
     try {

invoker/core/src/main/java/com/google/cloud/functions/invoker/HttpFunctionExecutor.java

@@ -61,8 +61,8 @@ public static HttpFunctionExecutor forClass(Class<?> functionClass) {
   }
 
   /** Executes the user's method, can handle all HTTP type methods. */
-  public void handle(String s, Request baseRequest, HttpServletRequest req,
-      HttpServletResponse res) throws IOException, ServletException {
+  public void handle(String s, Request baseRequest, HttpServletRequest req, HttpServletResponse res)
+      throws IOException, ServletException {
     baseRequest.setHandled(true);
     HttpRequestImpl reqImpl = new HttpRequestImpl(req);
     HttpResponseImpl respImpl = new HttpResponseImpl(res);

invoker/core/src/main/java/com/google/cloud/functions/invoker/TypedFunctionExecutor.java

@@ -98,8 +98,8 @@ static Optional<Type> handlerTypeArgument(Class<? extends TypedFunction<?, ?>> f
 
   /** Executes the user's method, can handle all HTTP type methods. */
   @Override
-  public void handle(String s, Request baseRequest, HttpServletRequest req,
-      HttpServletResponse res) throws IOException, ServletException {
+  public void handle(String s, Request baseRequest, HttpServletRequest req, HttpServletResponse res)
+      throws IOException, ServletException {
     baseRequest.setHandled(true);
     HttpRequestImpl reqImpl = new HttpRequestImpl(req);
     HttpResponseImpl resImpl = new HttpResponseImpl(res);

invoker/core/src/test/java/com/google/cloud/functions/invoker/http/HttpTest.java

@@ -108,9 +108,9 @@ private interface HttpRequestTest {
 
   /**
    * Tests methods on the {@link HttpRequest} object while the request is being serviced. We are not
-   * guaranteed that the underlying {@link Request} object will still be valid when the
-   * request completes, and in fact in Jetty it isn't. So we perform the checks in the context of
-   * the handler, and report any exception back to the test method.
+   * guaranteed that the underlying {@link Request} object will still be valid when the request
+   * completes, and in fact in Jetty it isn't. So we perform the checks in the context of the
+   * handler, and report any exception back to the test method.
    */
   @Test
   public void httpRequestMethods() throws Exception {
@@ -299,8 +299,11 @@ private HttpRequestHandler(
     }
 
     @Override
-    public void handle(String s, org.eclipse.jetty.server.Request baseRequest,
-        HttpServletRequest req, HttpServletResponse res)
+    public void handle(
+        String s,
+        org.eclipse.jetty.server.Request baseRequest,
+        HttpServletRequest req,
+        HttpServletResponse res)
         throws IOException, ServletException {
       baseRequest.setHandled(true);
       try {
@@ -382,8 +385,11 @@ private HttpResponseHandler(
     }
 
     @Override
-    public void handle(String s, org.eclipse.jetty.server.Request baseRequest,
-        HttpServletRequest req, HttpServletResponse resp) {
+    public void handle(
+        String s,
+        org.eclipse.jetty.server.Request baseRequest,
+        HttpServletRequest req,
+        HttpServletResponse resp) {
       try {
         baseRequest.setHandled(true);
         testReference.get().test(new HttpResponseImpl(resp));