[vm] Split canonical and non-canonical objects across clusters instead of within clusters.

Ensure canonical clusters come first; prep for canonical objects in snapshot accounting for the possibility an existing canonical object may substitute for them.

Bug: #41974
Change-Id: I8083f4130c359f0f86f73c25fa2869af672700e6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/164250
Reviewed-by: Régis Crelier <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google