Remove corelib/corelib_strong and migrate last two remaining tests.

tests/corelib_strong/regexp/v8_regexp_utils.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// Utility functions to easily port V8 tests.
-
-import "package:expect/expect.dart";
-
-void assertEquals(actual, expected, [String message = null]) {
-  Expect.equals(actual, expected, message);
-}
-
-void assertTrue(actual, [String message = null]) {
-  Expect.isTrue(actual, message);
-}
-
-void assertFalse(actual, [String message = null]) {
-  Expect.isFalse(actual, message);
-}
-
-void assertThrows(fn, [num testid = null]) {
-  Expect.throws(fn, null, "Test $testid");
-}
-
-void assertNull(actual, [num testid = null]) {
-  Expect.isNull(actual, "Test $testid");
-}
-
-void assertToStringEquals(str, match, num testid) {
-  var actual = [];
-  for (int i = 0; i <= match.groupCount; i++) {
-    var g = match.group(i);
-    actual.add((g == null) ? "" : g);
-  }
-  Expect.equals(str, actual.join(","), "Test $testid");
-}
-
-void shouldBeTrue(actual) {
-  Expect.isTrue(actual);
-}
-
-void shouldBeFalse(actual) {
-  Expect.isFalse(actual);
-}
-
-void shouldBeNull(actual) {
-  Expect.isNull(actual);
-}
-
-void shouldBe(actual, expected, [String message = null]) {
-  if (expected == null) {
-    Expect.isNull(actual, message);
-  } else {
-    Expect.equals(expected.length, actual.groupCount + 1);
-    for (int i = 0; i <= actual.groupCount; i++) {
-      Expect.equals(expected[i], actual.group(i), message);
-    }
-  }
-}
-
-Match firstMatch(String str, RegExp pattern) => pattern.firstMatch(str);
-List<String> allStringMatches(String str, RegExp pattern) =>
-    pattern.allMatches(str).map((Match m) => m.group(0)).toList();
-
-void description(str) {}