Mark only unreachable parts of element if it has reachable parts

like for 'return todo()' mark only 'return'

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/kt2585_1.kt

@@ -0,0 +1,12 @@
+//KT-2585 Code in try-finally is incorrectly marked as unreachable
+
+fun foo(x: String): String {
+    try {
+        <!UNREACHABLE_CODE!>throw<!> RuntimeException()
+    } finally {
+        try {
+        } catch (e: Exception) {
+        }
+        return x     // <- Wrong UNREACHABLE_CODE
+    }
+}