Introduce action to add missing when branches on sealed class

Made via diagnostics NON_EXHAUSTIVE_WHEN_FOR_SEALED_CLASS
with INFO severity and quick-fix
So #KT-17580 Fixed

compiler/testData/diagnostics/tests/when/NonExhaustiveWarningForSealedClass.kt

@@ -0,0 +1,16 @@
+sealed class S
+
+object First : S()
+
+class Derived(val s: String) : S()
+
+object Last : S()
+
+fun use(s: String) = s
+
+fun foo(s: S) {
+    <!NON_EXHAUSTIVE_WHEN_ON_SEALED_CLASS!>when<!> (s) {
+        First -> {}
+        is Derived -> use(<!DEBUG_INFO_SMARTCAST!>s<!>.s)
+    }
+}