JVM_IR: Specialize iterator if possible

fixes KT-47171

compiler/testData/codegen/box/forLoop/forInIterator.kt

@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JVM
+// WITH_STDLIB
+// CHECK_BYTECODE_LISTING
+
+fun myFun(iterator: MyUIntIterator) {
+    for (x in iterator) {
+        assert(x == 42u)
+    }
+}
+
+class MyUIntIterator : Iterator<UInt> {
+    private var count = 1
+    override fun hasNext(): Boolean = count-- > 0
+    override fun next(): UInt = 42u
+}
+
+fun box(): String {
+    myFun(MyUIntIterator())
+    return "OK"
+}
+
+// CHECK_BYTECODE_TEXT
+// JVM_IR_TEMPLATES
+// 0 java/util/Iterator.hasNext \(\)Z
+// 0 java/util/Iterator.next \(\)Ljava/lang/Object;
+// 1 MyUIntIterator.hasNext \(\)Z
+// 1 public synthetic bridge next\(\)Ljava/lang/Object;
+// 2 MyUIntIterator.next-pVg5ArA \(\)I

compiler/testData/codegen/box/forLoop/forInIterator.txt

@@ -0,0 +1,17 @@
+@kotlin.Metadata
+public final class ForInIteratorKt {
+    // source: 'forInIterator.kt'
+    public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
+    public final static method myFun(@org.jetbrains.annotations.NotNull p0: MyUIntIterator): void
+}
+
+@kotlin.Metadata
+public final class MyUIntIterator {
+    // source: 'forInIterator.kt'
+    private field count: int
+    public method <init>(): void
+    public method hasNext(): boolean
+    public synthetic bridge method next(): java.lang.Object
+    public method next-pVg5ArA(): int
+    public method remove(): void
+}