[OneSearch] Log events with timestamp into logcat for debugging.

Bug: 199289915
Test: example log: https://paste.googleplex.com/5741834610409472
Change-Id: I24b2e68b36cb897ae3e6ccc38cf0561d38af6751

src/com/android/launcher3/util/LogConfig.java

@@ -35,4 +35,9 @@ public class LogConfig {
      * When turned on, we enable doodle related logging.
      */
     public static final String DOODLE_LOGGING = "DoodleLogging";
+
+    /**
+     * When turned on, we enable suggest related logging.
+     */
+    public static final String SEARCH_LOGGING = "SearchLogging";
 }