[FIR] Assume smartacsts on member properties from friend modules as stable

^KT-57893 Fixed

compiler/testData/diagnostics/tests/smartCasts/smartcastInFriendModule.kt

@@ -0,0 +1,26 @@
+// ISSUE: KT-57893
+// MODULE: main
+internal class A {
+    val x: String? = null
+}
+
+class B {
+    internal val x: String? = null
+}
+
+class C {
+    val x: String? = null
+}
+
+// MODULE: test()(main)
+internal fun test(a: A, b: B, c: C) {
+    if (a.x != null) {
+        <!DEBUG_INFO_SMARTCAST!>a.x<!>.length
+    }
+    if (b.x != null) {
+        <!DEBUG_INFO_SMARTCAST!>b.x<!>.length
+    }
+    if (c.x != null) {
+        <!SMARTCAST_IMPOSSIBLE!>c.x<!>.length
+    }
+}