[FIR2IR] Generate IR declarations in classes in strict order

Order is following:
- declared declarations in declaration (in source) order
- generated declarations in sorted order

compiler/testData/ir/irText/classes/declarationOrder.kt

@@ -0,0 +1,19 @@
+// FIR_IDENTICAL
+// SKIP_KLIB_TEST
+// IGNORE_BACKEND_K1: JS_IR
+//   Ignore reason: there is a js name clash between function `a()` and property `a`
+package test
+
+class A() {
+    constructor(x: Int) : this()
+    fun b() {}
+    fun a() {}
+    val b: Int = 1
+    val a: Int = 2
+    constructor(x: String) : this()
+    val Int.b: String get() = "b"
+    fun String.b() {}
+    val Int.a: String get() = "a"
+    fun String.a() {}
+    constructor(x: Double) : this()
+}