Mixin kotlin.Number methods into j.l.Number member scope

#KT-9672 Fixed

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/MemberIndex.kt

@@ -42,7 +42,11 @@ object EMPTY_MEMBER_INDEX : MemberIndex {
 private val ADDITIONAL_MEMBER_NAMES_MAP = mapOf(
         FqName("java.util.List") to listOf(Name.identifier("removeAt")),
         FqName("java.lang.CharSequence") to listOf(Name.identifier("get")),
-        FqName("java.util.Map") to listOf(Name.identifier("keys"), Name.identifier("entries"))
+        FqName("java.util.Map") to listOf(Name.identifier("keys"), Name.identifier("entries")),
+        FqName("java.lang.Number") to listOf(
+                Name.identifier("toByte"), Name.identifier("toShort"), Name.identifier("toInt"), Name.identifier("toLong"),
+                Name.identifier("toFloat"), Name.identifier("toDouble")
+        )
 )
 
 open class ClassMemberIndex(val jClass: JavaClass, val memberFilter: (JavaMember) -> Boolean) : MemberIndex {

idea/idea-completion/testData/basic/java/Number.kt

@@ -0,0 +1,10 @@
+fun test(x: java.lang.Integer) {
+    x.<caret>
+}
+
+// EXIST: toByte
+// EXIST: toShort
+// EXIST: toInt
+// EXIST: toLong
+// EXIST: toFloat
+// EXIST: toDouble

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/JvmBasicCompletionTestGenerated.java

@@ -2302,6 +2302,12 @@ public class JvmBasicCompletionTestGenerated extends AbstractJvmBasicCompletionT
             doTest(fileName);
         }
 
+        @TestMetadata("Number.kt")
+        public void testNumber() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/java/Number.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("PackageDirective.kt")
         public void testPackageDirective() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/basic/java/PackageDirective.kt");