Add tests showing bug

Author: owen-mc

go/ql/test/query-tests/RedundantCode/UnreachableStatement/CONSISTENCY/CfgConsistency.expected

@@ -1,5 +1,5 @@
 consistencyOverview
-| deadEnd | 10 |
+| deadEnd | 11 |
 deadEnd
 | main.go:17:2:17:10 | select statement |
 | main.go:109:2:109:10 | select statement |
@@ -11,3 +11,4 @@ deadEnd
 | main.go:151:2:151:10 | select statement |
 | main.go:157:2:157:10 | select statement |
 | main.go:164:2:164:10 | select statement |
+| main.go:168:2:168:10 | select statement |

go/ql/test/query-tests/RedundantCode/UnreachableStatement/main.go

@@ -164,4 +164,19 @@ func test20() {
 	select {} // OK: reachable after starting the goroutine
 }
 
+func test21() {
+	select {}
+	panic("unreachable") // OK: allowlisted statement
+	// OK: empty statement
+	unreachable() // $ MISSING: Alert
+}
+
+func test23() {
+	if true {
+		return
+	}
+	unreachable() // OK: deliberately unreachable
+	unreachable() // OK: deliberately unreachable
+}
+
 func main() {}