test: Add a test that function argument patterns take in the expected type. r=test-only

src/test/run-pass/fn-pattern-expected-type.rs

+fn main() {
+    let f: fn((int,int)) = |(x, y)| {
+        assert x == 1;
+        assert y == 2;
+    };
+    f((1, 2));
+}
+