[Java][resttemplate] Add test for bearer auth (#17081)

* add bearer auth API to echo-api

* run generate-samples.sh

* add resttemplate echo-api sample

* add bearer auth test

* remove @Ignore

samples/client/echo_api/java/resttemplate/.gitignore

@@ -0,0 +1,21 @@
+*.class
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.ear
+
+# exclude jar for gradle wrapper
+!gradle/wrapper/*.jar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# build files
+**/target
+target
+.gradle
+build