IR API: change val ... : MutableList to var ...: List for most lists

All mutable state for IR declarations should be either:
- var (mutable properties)
- or class member list

Mutable properties are straightforward to persist.

The class member list is handled in a special way.

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/AnnotationGenerator.kt

@@ -40,8 +40,10 @@ class AnnotationGenerator(context: GeneratorContext) : IrElementVisitorVoid {
                 declaration.descriptor.backingField
             else declaration.descriptor
 
-        annotatedDescriptor?.annotations?.mapNotNullTo(declaration.annotations) {
-            constantValueGenerator.generateAnnotationConstructorCall(it)
+        if (annotatedDescriptor != null) {
+            declaration.annotations += annotatedDescriptor.annotations.mapNotNull {
+                constantValueGenerator.generateAnnotationConstructorCall(it)
+            }
         }
     }
 }

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt

@@ -87,7 +87,7 @@ class ClassGenerator(
         ).buildWithScope { irClass ->
             declarationGenerator.generateGlobalTypeParametersDeclarations(irClass, classDescriptor.declaredTypeParameters)
 
-            classDescriptor.typeConstructor.supertypes.mapTo(irClass.superTypes) {
+            irClass.superTypes = classDescriptor.typeConstructor.supertypes.map {
                 it.toIrType()
             }
 

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/DeclarationGenerator.kt

@@ -126,7 +126,7 @@ class DeclarationGenerator(override val context: GeneratorContext) : Generator {
         from: List<TypeParameterDescriptor>,
         declareTypeParameter: (Int, Int, TypeParameterDescriptor) -> IrTypeParameter
     ) {
-        from.mapTo(irTypeParametersOwner.typeParameters) { typeParameterDescriptor ->
+        irTypeParametersOwner.typeParameters += from.map { typeParameterDescriptor ->
             val ktTypeParameterDeclaration = DescriptorToSourceUtils.getSourceFromDescriptor(typeParameterDescriptor)
             val startOffset = ktTypeParameterDeclaration.startOffsetOrUndefined
             val endOffset = ktTypeParameterDeclaration.endOffsetOrUndefined

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/FunctionGenerator.kt

@@ -286,7 +286,7 @@ class FunctionGenerator(declarationGenerator: DeclarationGenerator) : Declaratio
         val bodyGenerator = createBodyGenerator(irFunction.symbol)
 
         // Declare all the value parameters up first.
-        functionDescriptor.valueParameters.mapTo(irFunction.valueParameters) { valueParameterDescriptor ->
+        irFunction.valueParameters += functionDescriptor.valueParameters.map { valueParameterDescriptor ->
             val ktParameter = DescriptorToSourceUtils.getSourceFromDescriptor(valueParameterDescriptor) as? KtParameter
             declareParameter(valueParameterDescriptor, ktParameter, irFunction)
         }

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ModuleGenerator.kt

@@ -71,7 +71,9 @@ class ModuleGenerator(override val context: GeneratorContext) : Generator {
 
         for (ktAnnotationEntry in ktFile.annotationEntries) {
             val annotationDescriptor = getOrFail(BindingContext.ANNOTATION, ktAnnotationEntry)
-            irFile.annotations.addIfNotNull(constantValueGenerator.generateAnnotationConstructorCall(annotationDescriptor))
+            constantValueGenerator.generateAnnotationConstructorCall(annotationDescriptor)?.let {
+                irFile.annotations += it
+            }
         }
 
         for (ktDeclaration in ktFile.declarations) {

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ReflectionReferencesGenerator.kt

@@ -379,7 +379,7 @@ class ReflectionReferencesGenerator(statementGenerator: StatementGenerator) : St
                     irAdapterFun.dispatchReceiverParameter = null
                     irAdapterFun.extensionReceiverParameter = null
 
-                    ktExpectedParameterTypes.mapIndexedTo(irAdapterFun.valueParameters) { index, ktExpectedParameterType ->
+                    irAdapterFun.valueParameters += ktExpectedParameterTypes.mapIndexed { index, ktExpectedParameterType ->
                         val adapterValueParameterDescriptor = WrappedValueParameterDescriptor()
                         context.symbolTable.declareValueParameter(
                             startOffset, endOffset,