Customers expect that when they add L2 resources directly to the Stack, the id they provide for the L2 will be the logical ID of the underlying L1 resource. This will also clean up the logical IDs of deCDK resource (#1618).

Aside from this being a huge breaking change, and we should probably allow people to disable this behavior for backwards compat. I don't see why we shouldn't implement this heuristic.

Change logical ID to "Default" (or ".") and then defaultChild (#2290) should be the way to access these resources.

@rix0rrr @RomainMuller @sam-goodwin what do you guys think?