Introduce special IrDeclarationOrigin's for for-loop variables

FOR_LOOP_ITERATOR
 - temporary variable for for-loop iterator

FOR_LOOP_VARIABLE
 - `x` in `for (x in xs)`

FOR_LOOP_IMPLICIT_VARIABLE
 - temporary variable for for-loop with destructuring, e.g.:
   for ((x, y) in xys)
   =>
   for (tmp in xys) {
     val (x, y) = tmp
   }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/builders/Scope.kt

@@ -50,9 +50,14 @@ class Scope(val scopeOwnerSymbol: IrSymbol) {
         return if (nameHint != null) "tmp${index}_$nameHint" else "tmp$index"
     }
 
-    fun createTemporaryVariable(irExpression: IrExpression, nameHint: String? = null, isMutable: Boolean = false): IrVariable =
+    fun createTemporaryVariable(
+            irExpression: IrExpression,
+            nameHint: String? = null,
+            isMutable: Boolean = false,
+            origin: IrDeclarationOrigin = IrDeclarationOrigin.IR_TEMPORARY_VARIABLE
+    ): IrVariable =
             IrVariableImpl(
-                    irExpression.startOffset, irExpression.endOffset, IrDeclarationOrigin.IR_TEMPORARY_VARIABLE,
+                    irExpression.startOffset, irExpression.endOffset, origin,
                     createDescriptorForTemporaryVariable(irExpression.type, nameHint, isMutable),
                     irExpression
             )

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrDeclarationOrigin.kt

@@ -19,6 +19,9 @@ package org.jetbrains.kotlin.ir.declarations
 interface IrDeclarationOrigin {
     object DEFINED : IrDeclarationOriginImpl("DEFINED")
     object FAKE_OVERRIDE : IrDeclarationOriginImpl("FAKE_OVERRIDE")
+    object FOR_LOOP_ITERATOR : IrDeclarationOriginImpl("FOR_LOOP_ITERATOR")
+    object FOR_LOOP_VARIABLE : IrDeclarationOriginImpl("FOR_LOOP_VARIABLE")
+    object FOR_LOOP_IMPLICIT_VARIABLE : IrDeclarationOriginImpl("FOR_LOOP_IMPLICIT_VARIABLE")
     object PROPERTY_BACKING_FIELD : IrDeclarationOriginImpl("PROPERTY_BACKING_FIELD")
     object DEFAULT_PROPERTY_ACCESSOR : IrDeclarationOriginImpl("DEFAULT_PROPERTY_ACCESSOR")
     object DELEGATE : IrDeclarationOriginImpl("DELEGATE")