[6.2] Cherry-pick "[test] Bring back accidentally deleted test case in..."

...#81280. The deleted test was
`test/FixCode/fixits-if-else.swift`. Resurrect it in a better place and
switch it to the diagnostic verifier, as it was intended to along with
other moved tests in that PR.

(cherry picked from commit 8928b53)

Author: AnthonyLatsis

test/Parse/if-else-invalid.swift

@@ -0,0 +1,44 @@
+// RUN: %target-swift-frontend -parse -verify %s
+
+// No more diags expected during Sema.
+// RUN: %target-typecheck-verify-swift
+
+do {
+  func something() -> Bool {}
+  func foo() {}
+
+  do {
+    if something() {
+    // expected-error@+1:11 {{expected '{' or 'if' after 'else'}}{{none}}
+    } else
+  }
+
+  do {
+    if something() {
+    // expected-error@+1:11 {{expected '{' or 'if' after 'else'}}{{none}}
+    } else
+    foo()
+  }
+
+  do {
+    if something() {
+    // expected-error@+1:7 {{expected '{' or 'if' after 'else'; did you mean to write 'if'?}}{{11-11= if}}
+    } else something() { // Fix-it because all on one line.
+    }
+  }
+
+  do {
+    if something() {
+    // expected-error@+1:12 {{expected '{' or 'if' after 'else'}}{{none}}
+    } else something()
+    {
+    }
+  }
+
+ do {
+    if something() {
+    // expected-error@+1:12 {{expected '{' or 'if' after 'else'}}{{none}}
+    } else something()
+    foo1()
+  }
+}