VM: Remove use of IterableMixinWorkaround from _List, _ImmutableList and _GrowableList.

_List, _ImmutableList and _GrowableList now extend ListBase which uses ListMixin.

Note that typed data lists are still using IterableMixinWorkaround for now.
They will be changed in a separate CL since it involves a few more changes
to the VM.

BUG=dartbug.com/13647
R=lrn@google.com

Review URL: https://codereview.chromium.org//730543002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@42061 260f80e4-7a28-3924-810f-c04153c831b5