[analyzer] Move late final tests into late_final_local_already_assigned_test.dart.

Some of the tests in `assignment_to_final_local_test.dart` were
actually testing `late final` locals, so they make more sense in
`late_final_local_already_assigned_test.dart`.

This paves the way for fixing
#60359 (Using a `late final`
variable as loop variable for `for`/`in` gives incorrect late errors).

Change-Id: I58da6ae6791adb1b124129b30b0d8c62bfa2d519
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/417000
Auto-Submit: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

pkg/analyzer/test/src/diagnostics/assignment_to_final_local_test.dart

@@ -26,7 +26,7 @@ f() {
     ]);
   }
 
-  test_localVariable_final_forEach() async {
+  test_localVariable_forEach() async {
     await assertErrorsInCode('''
 f() {
   final i;
@@ -51,29 +51,6 @@ f() {
     ]);
   }
 
-  test_localVariable_late() async {
-    await assertNoErrorsInCode('''
-void f() {
-  late final int a;
-  a = 1;
-  a;
-}
-''');
-  }
-
-  test_localVariable_lateFinal_forEach() async {
-    await assertErrorsInCode('''
-f() {
-  late final int i;
-  for (i in [1, 2, 3]) {
-    print(i);
-  }
-}
-''', [
-      error(CompileTimeErrorCode.LATE_FINAL_LOCAL_ALREADY_ASSIGNED, 33, 1),
-    ]);
-  }
-
   test_localVariable_plusEq() async {
     await assertErrorsInCode('''
 f() {

pkg/analyzer/test/src/diagnostics/late_final_local_already_assigned_test.dart

@@ -53,6 +53,29 @@ main() {
     ]);
   }
 
+  test_localVariable() async {
+    await assertNoErrorsInCode('''
+void f() {
+  late final int a;
+  a = 1;
+  a;
+}
+''');
+  }
+
+  test_localVariable_forEach() async {
+    await assertErrorsInCode('''
+f() {
+  late final int i;
+  for (i in [1, 2, 3]) {
+    print(i);
+  }
+}
+''', [
+      error(CompileTimeErrorCode.LATE_FINAL_LOCAL_ALREADY_ASSIGNED, 33, 1),
+    ]);
+  }
+
   test_postfixExpression_inc() async {
     await assertErrorsInCode('''
 main() {