Fix wrong nullability enhancement for annotated java.lang.Object type

Effectively, this commit drops cached value for j.l.Object type
This cache was introduced when types were immutable, but they
became mutable after starting reading top-level TYPE_USE annotations,
that lead to changing shared JAVA_LANG_OBJECT_CLASSIFIER_TYPE instance

 #KT-20826 Fixed

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/classFiles/BinaryClassSignatureParser.kt

@@ -16,14 +16,11 @@
 
 package org.jetbrains.kotlin.load.java.structure.impl.classFiles
 
-import com.intellij.psi.CommonClassNames
 import com.intellij.util.containers.ContainerUtil
 import org.jetbrains.kotlin.builtins.PrimitiveType
 import org.jetbrains.kotlin.load.java.structure.JavaClassifierType
 import org.jetbrains.kotlin.load.java.structure.JavaType
 import org.jetbrains.kotlin.load.java.structure.JavaTypeParameter
-import org.jetbrains.kotlin.name.ClassId
-import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.utils.addToStdlib.flattenTo
 import org.jetbrains.kotlin.utils.compact
@@ -33,14 +30,11 @@ import java.text.StringCharacterIterator
 
 /**
  * Take a look at com.intellij.psi.impl.compiled.SignatureParsing
+ * NOTE: currently this class can simply be converted to an object, but there are postponed plans
+ * to introduce cached instance for java.lang.Object type that would require injected class finder.
+ * So please, do not convert it to object
  */
-class BinaryClassSignatureParser(globalContext: ClassifierResolutionContext) {
-    companion object {
-        private val JAVA_LANG_OBJECT = ClassId.topLevel(FqName(CommonClassNames.JAVA_LANG_OBJECT))
-    }
-
-    private val JAVA_LANG_OBJECT_CLASSIFIER_TYPE: JavaClassifierType =
-            PlainJavaClassifierType({ globalContext.resolveClass(JAVA_LANG_OBJECT) }, emptyList())
+class BinaryClassSignatureParser {
 
     fun parseTypeParametersDeclaration(signature: CharacterIterator, context: ClassifierResolutionContext): List<JavaTypeParameter> {
         if (signature.current() != '<') {
@@ -68,25 +62,14 @@ class BinaryClassSignatureParser(globalContext: ClassifierResolutionContext) {
         val parameterName = name.toString()
 
         // postpone list allocation till a second bound is seen; ignore sole Object bound
-        var bounds: MutableList<JavaClassifierType>? = null
-        var jlo = false
+        val bounds: MutableList<JavaClassifierType> = ContainerUtil.newSmartList()
         while (signature.current() == ':') {
             signature.next()
             val bound = parseClassifierRefSignature(signature, context) ?: continue
-            if (bounds == null) {
-                if (JAVA_LANG_OBJECT_CLASSIFIER_TYPE === bound) {
-                    jlo = true
-                    continue
-                }
-                bounds = ContainerUtil.newSmartList()
-                if (jlo) {
-                    bounds.add(JAVA_LANG_OBJECT_CLASSIFIER_TYPE)
-                }
-            }
             bounds.add(bound)
         }
 
-        return BinaryJavaTypeParameter(Name.identifier(parameterName), bounds ?: emptyList())
+        return BinaryJavaTypeParameter(Name.identifier(parameterName), bounds)
     }
 
     fun parseClassifierRefSignature(signature: CharacterIterator, context: ClassifierResolutionContext): JavaClassifierType? {
@@ -148,8 +131,6 @@ class BinaryClassSignatureParser(globalContext: ClassifierResolutionContext) {
         }
         signature.next()
 
-        if (canonicalName.toString() == "java/lang/Object") return JAVA_LANG_OBJECT_CLASSIFIER_TYPE
-
         return PlainJavaClassifierType(
                 { context.resolveByInternalName(canonicalName.toString()) },
                 argumentGroups.reversed().flattenTo(arrayListOf()).compact()