Make AffixAllocator take into account RCISharedAllocator

[edi33416]

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[edi33416]

@jercaianu

[edi33416]

I've moved the parent() logic inside the mixin template Impl as this also needs to infer the shared attribute.

[edi33416]

@n8sh could you have another look at the code? Changed sync to use only one variable

[RazvanN7]

@edi33416 What is the state of this PR? Should we pull it in?