fix(opentelemetry): update method names of sprring controllers to match the javadoc (GoogleCloudPlatform#8973)

Author: aabmass

opentelemetry/spring-boot-instrumentation/src/main/java/com/example/demo/MultiController.java

@@ -40,7 +40,7 @@ public class MultiController {
    * span for the controller body.
    */
   @GetMapping("/multi")
-  public Mono<String> index() throws Exception {
+  public Mono<String> handleMulti() throws Exception {
     int subRequests = ThreadLocalRandom.current().nextInt(3, 8);
 
     // Write a structured log with the request context, which allows the log to

opentelemetry/spring-boot-instrumentation/src/main/java/com/example/demo/SingleController.java

@@ -35,7 +35,7 @@ public class SingleController {
    * span for the controller body.
    */
   @GetMapping("/single")
-  public String index() throws InterruptedException {
+  public String handleSingle() throws InterruptedException {
     int sleepMillis = ThreadLocalRandom.current().nextInt(100, 200);
     logger.info("Going to sleep for {}", sleepMillis);
     Thread.sleep(sleepMillis);