[vm/concurrency] Make Dart_CreateIsolateInGroup() return an error if --enable-isolate-groups is not passed

This is a safeguard to prevent accidental uses of this API by embedders
if those embedders do not pass --enable-isolate-groups.

Issue https://github.com/dart-lang/sdk/issues/36097

TEST=runtime/tests/vm/dart/isolates/dart_api_create_lightweight_isolate_test.dart

Change-Id: Iba667f0e9fbbb33de963fabb80da546df794257c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/174404
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>

https://dart.googlesource.com/sdk/+/33b7721c51ad499f8a6adf9c0366ca1bfcbbe84b
diff --git a/commits.json b/commits.json
index 5e2327a..d40c515 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "external/github.com/flutter/engine":"a4ce848dfb6fb002544494e762f53a826830cc1d",
   "external/github.com/flutter/flutter":"a7f5fd5360007518644597c60a1f2169eacccc2b",
-  "sdk":"58860f4814fb8bd36d0ebd580425a773ea7ede8c"
+  "sdk":"33b7721c51ad499f8a6adf9c0366ca1bfcbbe84b"
 }
\ No newline at end of file