Teach index working with source roots with package prefix

#KT-9167 Fixed

Original commit: 23e35ab112

jps/jps-plugin/testData/general/SourcePackagePrefix/src/OtherJava.java

@@ -0,0 +1,4 @@
+package xxx;
+
+public class OtherJava {
+}

jps/jps-plugin/testData/general/SourcePackagePrefix/src/Test.java

@@ -0,0 +1,7 @@
+package xxx;
+
+public class Test {
+    String test(OtherJava otherJava) {
+        return "";
+    }
+}

jps/jps-plugin/testData/general/SourcePackagePrefix/src/test.kt

@@ -0,0 +1,3 @@
+package xxx
+
+val test = Test().test(null)