Deprecate simplification of complex boolean constant expressions in whens and loops

^KT-39883 In Progress

compiler/testData/diagnostics/tests/smartCasts/loops/whileTrivial.fir.kt

@@ -0,0 +1,12 @@
+// LANGUAGE: -ProhibitSimplificationOfNonTrivialConstBooleanExpressions
+fun x(): Boolean { return true }
+
+public fun foo(p: String?): Int {
+    // Like whileTrue but 2 == 2 is in use
+    while(2 == 2) {
+        p!!.length
+        if (x()) break
+    }
+    // Smart cast should not work in this case, see KT-6284
+    return p<!UNSAFE_CALL!>.<!>length
+}