JVM_IR KT-47326 downcast field receiver on JvmField lowering

compiler/testData/codegen/box/jvmField/kt47328_var.kt

@@ -0,0 +1,22 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+
+interface A { var x: Int }
+
+class B(@JvmField override var x: Int): A
+
+class C<D: A>(@JvmField val d: D)
+
+class E(c: C<B>) {
+    init {
+        c.d.x = 42
+    }
+    val ax = c.d.x
+}
+
+fun box(): String {
+    val e = E(C(B(1234)))
+    if (e.ax != 42)
+        return "Failed: ${e.ax}"
+    return "OK"
+}