Combined identifier info for things like '(x + y).z' is no longer treated as 'z' identifier info + a pair of tests + code fix #KT-9126 Fixed

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

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNNECESSARY_NOT_NULL_ASSERTION
+// See KT-9126: Variable change does not affect data flow info for its fields
+
+class My(val x: Int?)
+
+fun foo() {
+    var y: My? = My(42)
+    if (y!!.x != null) {
+        y = My(null)
+        y!!.x<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}