[FIR2IR] Introduce staged transformation (first step)

Now FE IR -> BE IR transformation is performed in multiple stages
controller by Fir2IrConverter. Stages are
 * files & classes registration
 * supertypes & type parameters handling
 * functions & properties signature generation
 * body generation

After each step we have guarantee (with exception of local classes &
type inference combination, and external symbols) that required symbols
(class/function/property/variable/type parameter)
are already bound to real declarations and have correct parents.

This commit also fixes incorrect parents for local classes

compiler/testData/codegen/box/objects/companionObjectAccess/multipleCompanionsWithAccessors/fromAnonymousObjectInNestedClass.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +ProperVisibilityForCompanionObjectInstanceField
-// IGNORE_BACKEND_FIR: JVM_IR
 // FILE: fromAnonymousObjectInNestedClass.kt
 import outer.*
 

compiler/testData/codegen/box/objects/companionObjectAccess/privateCompanionObjectAccessedFromAnonymousObjectInNestedClass.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +ProperVisibilityForCompanionObjectInstanceField
-// IGNORE_BACKEND_FIR: JVM_IR
 
 class Outer {
     private companion object {

compiler/testData/codegen/box/objects/objectInLocalAnonymousObject.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun box(): String {
     var boo = "OK"
     var foo = object {

compiler/testData/codegen/box/objects/objectLiteralInClosure.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 package p
 
 private class C(val y: Int) {

compiler/testData/codegen/box/objects/receiverInConstructor.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 open class A(open val v: String)
 
 fun A.a(newv: String) = object: A("fail") {