Rename package in JPS plugin tests

Package 'kotlin' is not supported until package views are implemented, because
its name clashes with the stdlib

jps-plugin/testData/KJKInheritanceProject/src/java/JFirst.java

@@ -1,4 +1,4 @@
 package java;
 
-public class JFirst extends kotlin.KFirst {
-}
+public class JFirst extends kt.KFirst {
+}

jps-plugin/testData/KJKInheritanceProject/src/kotlin/KFirst.kt

@@ -1,6 +1,6 @@
-package kotlin
+package kt
 
 open class KFirst() {
     fun foo() {
     }
-}
+}

jps-plugin/testData/KJKInheritanceProject/src/kotlin/KSecond.kt

@@ -1,7 +1,7 @@
-package kotlin
+package kt
 
 class KSecond(): java.JFirst() {
     fun bar() {
         foo()
     }
-}
+}