Reclaim the CreatedFromSnapshot bit and use it to indicate VM Heap object

tests/isolate/isolate.status

 # Copyright (c) 2012, 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.
 
 [ $runtime == vm ]
 browser/*: SkipByDesign  # Browser specific tests
 isolate_stress_test: Fail # Issue 12588: This should be able to pass when we have wrapper-less tests.
 
 [ $runtime != vm ]
 checked_test: Skip # Unsupported.
 
 [ $runtime == vm && $arch == mips && $mode == debug ]
 mandel_isolate_test: Skip # Uses 600 MB Ram on our 1 GB test device.
 
 [ $compiler == none ]
 compile_time_error_test/01: Skip # Issue 12587
 ping_test: Skip           # Resolve test issues
 ping_pause_test: Skip     # Resolve test issues
 kill3_test: Pass, Fail    # Bad test: expects total message order
 
-message3_test/constList_identical: RuntimeError # Issue 21816
-message3_test/constMap: RuntimeError  # Issue 21816
-message3_test/constInstance: RuntimeError # Issue 21816
 message3_test/byteBuffer: Crash # Issue 21818
 message3_test/int32x4: Crash # Issue 21818
 
 [ $compiler == none && $runtime == ContentShellOnAndroid ]
 *: Skip # Isolate tests are timing out flakily on Android content_shell.  Issue 19795
 
 [ $compiler == dart2js && $runtime == safarimobilesim ]
 compile_time_error_test/none: Pass, Slow
 
 [ $compiler == dart2js && $jscl ]
@@ skipping 109 matching lines @@
 [ $compiler != none || $runtime != vm ]
 package_root_test: SkipByDesign # Uses dart:io.
 
 [ $compiler == dart2js && $cps_ir ]
 deferred_in_isolate2_test: Crash # (lib.f()): deferred access is not implemented
 isolate_current_test: RuntimeError # Please triage this failure.
 message3_test/byteBuffer: RuntimeError # Please triage this failure.
 message3_test/fun: RuntimeError # Please triage this failure.
 message3_test/int32x4: RuntimeError # Please triage this failure.
 message3_test/none: RuntimeError # Please triage this failure.