Union this-types of unioned call signatures

And and tests and baselines

tests/cases/conformance/types/thisType/unionThisTypeInFunctions.ts

@@ -0,0 +1,12 @@
+// @strictThis: true
+interface Real {
+    method(n: number): void;
+    data: string;
+}
+interface Fake {
+    method(n: number): void;
+    data: number;
+}
+function test(r: Real | Fake) {
+    r.method(12);
+}