Add Echo Parameter In Android App

Summary:
If echo = true then token_callback for output will also include input (i.e. Text Completition)

If echo = false then token_callback for output will not include input (i.e. Chat generation).

We'll default to true since that will maintain the existing flow.

Differential Revision: D61394870

Author: cmodi-meta

examples/demo-apps/android/LlamaDemo/app/src/main/java/com/example/executorchllamademo/MainActivity.java

@@ -599,7 +599,7 @@ public void run() {
                       });
                   ETLogging.getInstance().log("Running inference.. prompt=" + prompt);
                   long generateStartTime = System.currentTimeMillis();
-                  mModule.generate(prompt, MainActivity.this);
+                  mModule.generate(prompt, false, MainActivity.this);
                   long generateDuration = System.currentTimeMillis() - generateStartTime;
                   mResultMessage.setTotalGenerationTime(generateDuration);
                   runOnUiThread(