Registration source handling differs based on how child scopes are created

[tillig]

Not really a bug or a feature, but something we should check into: When you call LifetimeScope.BeginLifetimeScope() the handling of how registration sources are dealt with differs based on whether you pass a configuration action. Specifically, in that case any registration source where IsAdapterForIndividualComponent is true will be copied into the child lifetime scope.

This can cause duplicate resolutions to occur as seen in autofac/Autofac.Mef#23.

With the major amount of change that's gone on in v6.x it may be worth checking into whether the IsAdapterForIndividualComponent flag makes sense anymore; and possibly whether we're handling registration sources properly in each case, assuming it is.

[tillig]

We're pretty far past this and I don't think anyone is going to do anything here. If we see a PR to address some of this, great; if not, it'll be what it is.